[One (M8) Android Development] simonvfr:
And here's more logging, showing NFC on/off and a pairing with headset:

10-08 12:23:33.848 W/PackageManager(743): Unknown permission android.permission.NFC_UNLOCK in package com.android.nfc
10-08 12:23:35.379 D/BackupManagerService(743): Now staging backup of com.android.nfc
10-08 12:23:35.800 I/ActivityManager(743): Start proc 1042:com.android.nfc/1027 for service com.android.nfc/.NfcBootstrapService
10-08 12:23:38.398 W/PackageManager(743): Unknown permission android.permission.NFC_UNLOCK in package com.android.nfc
10-08 12:30:05.185 D/NfcService(1042): Discovery configuration equal, not updating.
10-08 12:33:10.823 I/NfcService(1042): Disabling NFC
10-08 12:33:10.823 D/WirelessSettings(11332): onPreferenceTreeClick: preference=NFC Allow data exchange when the phone touches another device
10-08 12:33:10.824 D/NfcP2pLinkManager(1042): enableDisable: llcp deactivate
10-08 12:33:10.824 I/NfcP2pLinkManager(1042): LLCP deactivated.
10-08 12:33:10.824 I/NfcP2pLinkManager(1042): Duplicate onLlcpDectivated()
10-08 12:33:10.900 D/NFCJNI (1042): Terminating client thread...
10-08 12:33:10.952 D/NFCJNI (1042): phLibNfc_Mgt_UnConfigureDriver() returned 0x0000[NFCSTATUS_SUCCESS]
10-08 12:34:18.838 I/NfcService(1042): Enabling NFC
10-08 12:34:18.838 D/WirelessSettings(11332): onPreferenceTreeClick: preference=NFC Allow data exchange when the phone touches another device
10-08 12:34:18.839 D/NFCJNI (1042): Start Initialization
10-08 12:34:19.021 E/NFC-HCI (1042): Could not open /vendor/firmware/libpn544_fw.so or /system/lib/libpn544_fw.so
10-08 12:34:19.599 W/NFC (1042): Firmware image not available: this device might be running old NFC firmware!
10-08 12:34:19.599 D/NFCJNI (1042): NFC capabilities: HAL = 8150100, FW = b10129, HW = 620003, Model = 11, HCI = 1, Full_FW = 1, Rev = 41, FW Update Info = 0
10-08 12:34:19.719 D/NFCJNI (1042): phLibNfc_SE_GetSecureElementList()
10-08 12:34:19.719 D/NFCJNI (1042):
10-08 12:34:19.719 D/NFCJNI (1042): > Number of Secure Element(s) : 1
10-08 12:34:19.719 D/NFCJNI (1042): phLibNfc_SE_GetSecureElementList(): SMX detected, handle=0xabcdef
10-08 12:34:19.719 D/NFCJNI (1042): phLibNfc_SE_SetMode() returned 0x000d[NFCSTATUS_PENDING]
10-08 12:34:19.743 I/NFCJNI (1042): NFC Initialized
10-08 12:34:19.928 I/FFMPEG (318): TITLE : NFCSuccess
10-08 12:34:20.016 I/FFMPEG (318): TITLE : NFCSuccess
10-08 12:34:20.089 I/FFMPEG (318): TITLE : NFCFailure
10-08 12:37:45.174 D/WirelessSettings(11332): onPreferenceTreeClick: preference=NFC Allow data exchange when the phone touches another device
10-08 12:37:45.175 I/NfcService(1042): Disabling NFC
10-08 12:37:45.177 D/NfcP2pLinkManager(1042): enableDisable: llcp deactivate
10-08 12:37:45.177 I/NfcP2pLinkManager(1042): LLCP deactivated.
10-08 12:37:45.177 I/NfcP2pLinkManager(1042): Duplicate onLlcpDectivated()
10-08 12:37:45.250 D/NFCJNI (1042): Terminating client thread...
10-08 12:37:45.302 D/NFCJNI (1042): phLibNfc_Mgt_UnConfigureDriver() returned 0x0000[NFCSTATUS_SUCCESS]
10-08 12:40:36.426 D/WirelessSettings(11332): onPreferenceTreeClick: preference=NFC Allow data exchange when the phone touches another device
10-08 12:40:36.427 I/NfcService(1042): Enabling NFC
10-08 12:40:36.428 D/NFCJNI (1042): Start Initialization
10-08 12:40:36.603 E/NFC-HCI (1042): Could not open /vendor/firmware/libpn544_fw.so or /system/lib/libpn544_fw.so
10-08 12:40:37.137 W/NFC (1042): Firmware image not available: this device might be running old NFC firmware!
10-08 12:40:37.137 D/NFCJNI (1042): NFC capabilities: HAL = 8150100, FW = b10129, HW = 620003, Model = 11, HCI = 1, Full_FW = 1, Rev = 41, FW Update Info = 0
10-08 12:40:37.240 D/NFCJNI (1042): phLibNfc_SE_GetSecureElementList()
10-08 12:40:37.240 D/NFCJNI (1042):
10-08 12:40:37.240 D/NFCJNI (1042): > Number of Secure Element(s) : 1
10-08 12:40:37.240 D/NFCJNI (1042): phLibNfc_SE_GetSecureElementList(): SMX detected, handle=0xabcdef
10-08 12:40:37.240 D/NFCJNI (1042): phLibNfc_SE_SetMode() returned 0x000d[NFCSTATUS_PENDING]
10-08 12:40:37.265 I/NFCJNI (1042): NFC Initialized
10-08 12:40:37.283 I/FFMPEG (318): TITLE : NFCSuccess
10-08 12:40:37.343 I/FFMPEG (318): TITLE : NFCSuccess
10-08 12:40:37.406 I/FFMPEG (318): TITLE : NFCFailure
10-08 12:41:53.112 I/FFMPEG (318): TITLE : NFCSuccess
10-08 12:41:53.206 I/Timeline(1042): Timeline: Activity_launch_request id:com.android.nfc time:1041704
10-08 12:41:53.207 I/ActivityManager(743): START u0 {flg=0x10000000 cmp=com.android.nfc/.handover.ConfirmConnectActivity (has extras)} from uid 1027 on display 0
10-08 12:41:53.215 V/WindowManager(743): addAppToken: AppWindowToken{1bf19369 token=Token{29f931f0 ActivityRecord{30faa33 u0 com.android.nfc/.handover.ConfirmConnectActivity t2886}}} to stack=1 task=2886 at 0
10-08 12:41:53.332 V/WindowManager(743): Adding window Window{1c06fd25 u0 com.android.nfc/com.android.nfc.handover.ConfirmConnectActivity} at 8 of 14 (after Window{fbc007d u0 com.nolanlawson.logcat/com.nolanlawson.logcat.LogcatActivity})
10-08 12:41:53.338 V/WindowManager(743): Adding window Window{26c2cab u0 com.android.nfc/com.android.nfc.handover.ConfirmConnectActivity} at 8 of 15 (before Window{1c06fd25 u0 com.android.nfc/com.android.nfc.handover.ConfirmConnectActivity})
10-08 12:41:53.341 D/NativeNfcTag(1042): Tag lost, restarting polling loop
10-08 12:41:53.342 D/NfcService(1042): Discovery configuration equal, not updating.
10-08 12:41:53.434 I/ActivityManager(743): Displayed com.android.nfc/.handover.ConfirmConnectActivity: +140ms
10-08 12:41:53.612 I/Timeline(743): Timeline: Activity_windows_visible id: ActivityRecord{30faa33 u0 com.android.nfc/.handover.ConfirmConnectActivity t2886} time:1042110
10-08 12:41:55.806 I/Service (1859): Notification from Nfc Service ignored for reason(s): Ignored app
10-08 12:42:00.704 I/Service (1859): Notification from Nfc Service ignored for reason(s): Ignored app
10-08 12:42:02.693 I/Service (1859): Notification from Nfc Service ignored for reason(s): Ignored app

Can't pretend to understand it! And there's clearly some errors in there.

Hopefully, it will help. And it will be interesting if others can check.