[OnePlus 8T Questions & Answers] Boing7898:
Hi guys. My Oneplus 8T lately has been having this weird issue where internet with 5 GHz WiFi stops working showing "no internet" and then my 5 GHz network disappears, alongside all other 5 GHz networks. I checked this with WiFi Analyzer and no 5 GHz network pops up. Toggling airplane mode does not fix the problem, only a full reboot does, and then my phone can see all 5 GHz networks present again.

It's not a problem with my router because other devices can see and connect to the 5 GHz network with no problem, only my 8T has this issue. First time I had this issue I was on Lineage 20, then I completely returned the phone to stock with msmtool on OxygenOS 11 and updated it to OxygenOS 14 where today, after 4 days of no problems, I encountered the issue again. I thought it was a problem with a ROM/firmware but apparently it's something deeper.

I tried to get some logs from logcat but there's constant spam and it's hard to get something useful, but this might be relevant:

03-11 18:57:36.546 1720 1747 W System : A resource failed to call close.
03-11 18:57:36.557 1720 3045 E WifiScoringParams: Invalid frequency(-1), using 5G as default rssi array
03-11 18:57:36.873 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact
03-11 18:57:37.449 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact
03-11 18:57:38.305 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact
03-11 18:57:39.734 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact
03-11 18:57:40.108 1077 1141 E TetherController: addInterface wlan0->22 succ
03-11 18:57:40.111 3229 3248 E Diag_Lib: [IMS_AP]"ims-rtp-daemon ims_rtp_qmi_handler_thread_func waiting on select thread>"
03-11 18:57:40.111 1077 1141 E TetherController: addInterface wlan0->22 succ
03-11 18:57:40.113 3229 3248 E Diag_Lib: [IMS_AP]"ims-rtp-daemon ims_rtp_qmi_handler_thread_func waiting on select thread>"
03-11 18:57:40.113 1720 3045 W LastMileLogger: Failed to open free_buffer pseudo-file: /sys/kernel/debug/tracing/instances/wifi/free_buffer: open failed: ENOENT (No such file or directory)
03-11 18:57:40.113 1720 3045 W LastMileLogger: Failed to arm fail-safe.
03-11 18:57:40.115 1077 1141 E TetherController: addInterface wlan0->22 succ
03-11 18:57:40.115 3229 3248 E Diag_Lib: [IMS_AP]"ims-rtp-daemon ims_rtp_qmi_handler_thread_func waiting on select thread>"
03-11 18:57:40.120 1952 1952 W wificond: Scan is not started. Ignore abort request
03-11 18:57:40.127 5958 6025 E OsAgent : wifiInfo/supplicantState returned null
03-11 18:57:40.128 1720 3045 W ContextImpl: Calling a method in the system process without a qualified user: android.app.ContextImpl.sendStickyBroadcast:1630 com.android.server.wifi.ClientModeImpl.sendNetworkChangeBroadcast:3008 com.android.server.wifi.ClientModeImpl.lambda$sendNetworkChangeBroadcastWithCurrentState$14:2985 com.android.server.wifi.ClientModeImpl.$r8$lambda$q-j88Pjw4gROgoJFr8wBlBVbuJI:0 com.android.server.wifi.ClientModeImpl$$ExternalSyntheticLambda4.send:0
03-11 18:57:40.129 5958 6025 E OsAgent : wifiInfo/supplicantState returned null
03-11 18:57:40.129 5958 6025 E OsAgent : wifiInfo/supplicantState returned null
03-11 18:57:40.134 1720 1720 E OplusOshareStats: Received broadcast:android.net.wifi.STATE_CHANGE
03-11 18:57:40.140 3939 3939 W BluetoothAdapterService: fetchWifiState - isWifiConnected =false
03-11 18:57:40.583 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact
03-11 18:57:40.740 3441 3441 W SystemUi--Keyguard: ChargingAnimationImpl-->BatteryStatus is same as last time , return
03-11 18:57:40.740 6484 6484 E VendorNfcService: changeNfcStateByWirelessCharge: feature WIRELESS_CHARGING = true; mIsWirelessCharging: false; mIsReverseChargingSwitchOpen: false; mNfcWorkMode: 0; isOverSeaRegion() = true
03-11 18:57:40.743 6549 7552 E Battery : ChargeProtectionUtils: mCanlendarTmp.isEmpty()!
03-11 18:57:41.152 3939 5240 E adv_data_processor: adv data modified, but len check fail or data invalid, stay intact

If more logs are needed just ask, I can debug as long as I don't reboot my phone. I really hope it's not a hardware problem but it really looks like one.

Thank you guys!