[Galaxy Note 4 Android Development (Snapdragon)] linqdesires:
Which N4 version do you have?

If N910F can you please share your modem/bootloader version?

My cell radio become unavailable suddenly, this is from my modem log:

03-15 21:28:25.047 D/RILJ ( 1133): [2428]> RIL_REQUEST_SEND_DEVICE_STATE 2:false [SUB0]
03-15 21:28:25.047 D/RILJ ( 1133): [2429]> RIL_REQUEST_SET_UNSOLICITED_RESPONSE_FILTER 7 [SUB0]
03-15 21:28:25.047 D/RILC (26208): sendDeviceState: calling screen state 1
03-15 21:28:25.052 E/RILD (26208): RefreshRegion: mCscSalesCode(), mCscCountry(), mCscCountry()
03-15 21:28:25.052 E/RILD (26208): RefreshRegion: mOmcSalesCode(), mOmcCountry(), mOmcCountryISO()
03-15 21:28:25.052 E/RILD (26208): IsRegisteredNetworkType(): netType[1] feature[00] state[0]
03-15 21:28:25.053 D/RILJ ( 1133): [2428]< RIL_REQUEST_SEND_DEVICE_STATE error 1 [SUB0]
03-15 21:28:25.053 D/RilRequest( 1133): [2428]< RIL_REQUEST_SEND_DEVICE_STATE error: com.android.internal.telephony.CommandException: RADIO_NOT_AVAILABLE ret=
03-15 21:28:25.054 D/RILJ ( 1133): [2429]< RIL_REQUEST_SET_UNSOLICITED_RESPONSE_FILTER error 6 [SUB0]
03-15 21:28:25.054 D/RilRequest( 1133): [2429]< RIL_REQUEST_SET_UNSOLICITED_RESPONSE_FILTER error: com.android.internal.telephony.CommandException: REQUEST_NOT_SUPPORTED ret=
03-15 21:28:25.339 D/DCT ( 1133): [0]screen on
03-15 21:28:25.339 D/DCT ( 1133): [0]stopNetStatPoll
03-15 21:28:28.176 D/RILJ ( 1133): [2430]> RIL_REQUEST_GET_CELL_INFO_LIST [SUB0]
03-15 21:28:28.176 E/RILD (26208): RefreshRegion: mCscSalesCode(), mCscCountry(), mCscCountry()
03-15 21:28:28.176 E/RILD (26208): RefreshRegion: mOmcSalesCode(), mOmcCountry(), mOmcCountryISO()
03-15 21:28:28.176 E/RILD (26208): IsRegisteredNetworkType(): netType[1] feature[00] state[0]
03-15 21:28:28.177 D/RILJ ( 1133): [2430]< RIL_REQUEST_GET_CELL_INFO_LIST error 1 [SUB0]
03-15 21:28:28.177 D/RilRequest( 1133): [2430]< RIL_REQUEST_GET_CELL_INFO_LIST error: com.android.internal.telephony.CommandException: RADIO_NOT_AVAILABLE ret=[]

About front camera crash: is not happening on Footeji ok, but I want to contribute with some logs.

Stock camera app, front camera crash

03-15 22:16:28.018 D/CAM_PhotoModule(30873): updateCameraParametersPreference final preview size = 1920, 1080
03-15 22:16:28.018 V/CAM_PhotoModule(30873): Preview size is 1920x1080
03-15 22:16:28.018 V/CAM_PhotoModule(30873): Thumbnail size is 512x288
03-15 22:16:28.019 D/AndroidRuntime(30873): Shutting down VM
03-15 22:16:28.028 E/AndroidRuntime(30873): FATAL EXCEPTION: main
03-15 22:16:28.028 E/AndroidRuntime(30873): Process: org.lineageos.snap, PID: 30873
03-15 22:16:28.028 E/AndroidRuntime(30873): java.lang.RuntimeException: Unexpected Jpeg encoding quality levels 0
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.media.CameraProfile.getImageEncodingQualityLevels(CameraProfile.java:99)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.media.CameraProfile.getJpegEncodingQualityParameter(CameraProfile.java:84)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.updateCameraParametersPreference(PhotoModule.java:4365)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.setCameraParameters(PhotoModule.java:4520)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.startPreview(PhotoModule.java:3254)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.setupPreview(PhotoModule.java:3209)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.switchCamera(PhotoModule.java:816)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoModule.onCameraPickerClicked(PhotoModule.java:5162)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.camera.PhotoMenu$4.onClick(PhotoMenu.java:892)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.view.View.performClick(View.java:6294)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.view.View$PerformClick.run(View.java:24770)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.os.Handler.handleCallback(Handler.java:790)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.os.Handler.dispatchMessage(Handler.java:99)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.os.Looper.loop(Looper.java:164)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at android.app.ActivityThread.main(ActivityThread.java:6494)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at java.lang.reflect.Method.invoke(Native Method)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:440)
03-15 22:16:28.028 E/AndroidRuntime(30873):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
03-15 22:16:27.825 I/chatty ( 810): uid=1000(system) Binder:810_B identical 4 lines
03-15 22:16:28.017 W/BackupManagerService( 810): dataChanged but no participant pkg='org.lineageos.snap' uid=10024
03-15 22:16:28.049 W/ActivityManager( 810): Force finishing activity org.lineageos.snap/com.android.camera.CameraActivity
03-15 22:16:28.056 I/ActivityManager( 810): Showing crash dialog for package org.lineageos.snap u0

Opencamera, front camera crash

03-15 21:54:03.294 W/QCamera2HWI( 494): [KPI Perf] set_parameters : X, ret 0
03-15 21:54:03.294 E/MediaProfiles(28739): The given camcorder profile camera 1 quality 1 is not found
03-15 21:54:03.294 I/chatty (28739): uid=10139(net.sourceforge.opencamera) identical 9 lines
03-15 21:54:03.294 E/MediaProfiles(28739): The given camcorder profile camera 1 quality 1 is not found
03-15 21:54:03.297 D/AndroidRuntime(28739): Shutting down VM
03-15 21:54:03.301 E/AndroidRuntime(28739): FATAL EXCEPTION: main
03-15 21:54:03.301 E/AndroidRuntime(28739): Process: net.sourceforge.opencamera, PID: 28739
03-15 21:54:03.301 E/AndroidRuntime(28739): java.lang.RuntimeException: Error retrieving camcorder profile params
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.media.CamcorderProfile.native_get_camcorder_profile(Native Method)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.media.CamcorderProfile.get(CamcorderProfile.java:398)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.getVideoProfile(Preview.java:2692)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.setPreviewFps(Preview.java:3606)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.startCameraPreview(Preview.java:5465)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.setupCamera(Preview.java:1724)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.cameraOpened(Preview.java:1530)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview.access$800(Preview.java:92)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview$1.onPostExecute(Preview.java:1383)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at net.sourceforge.opencamera.Preview.Preview$1.onPostExecute(Preview.java:1366)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.os.AsyncTask.finish(AsyncTask.java:695)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.os.AsyncTask.-wrap1(Unknown Source:0)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:712)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.os.Handler.dispatchMessage(Handler.java:106)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.os.Looper.loop(Looper.java:164)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at android.app.ActivityThread.main(ActivityThread.java:6494)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at java.lang.reflect.Method.invoke(Native Method)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:440)
03-15 21:54:03.301 E/AndroidRuntime(28739):	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
03-15 21:54:03.349 W/ActivityManager( 810): Force finishing activity net.sourceforge.opencamera/.MainActivity

On logcat I can even spot a lot of these:

03-15 20:11:23.863 W/wificond( 496): Skip match ssid for pno scan: mywifiregistered1, mywifiregistered2, mywifiregistered3, c4
03-15 20:11:23.863 E/wificond( 496): NL80211_CMD_START_SCHED_SCAN failed: Operation not supported on transport endpoint
03-15 20:11:23.863 E/wificond( 496): Failed to start pno scan

With mywifiregistered being the name of a wifi for which I saved credentials.