After re-flashing and reinstalling everything (just to be safe), still same problems.
Before this issue, I had everything running wonderfully for months - LTE (three.co.uk) only, no landline whatsoever. Then, ‘possibly, but not necessarily’ after an auto update, the connection would vanish after a few minutes of up-time. A reboot would not fix it, but a pull/reconnect of the mains plug would restore the connection for a few minutes before dropping again. This afternoon, I was able to connect, ping and download a 50MB file before the connection dropped after 5 minutes.
System log would be extremely lengthy, as the Quectel EC25-E Mini PCIe modem keeps on trying to reconnect. After pulling/re-plugging the power, and being able connect to the Internet for a few minutes, it then drops again, and the following sequence is repeated by the modem ad infinitum with no connection being established, unless you pull/re-plug the power yet again.
Aug 12 14:46:04 bard netifd: Interface ‘lte’ is setting up now
Aug 12 14:46:06 bard netifd: lte (20208): ppp: warning: Sleeping for ‘10’ seconds
Aug 12 14:46:16 bard pppd[20315]: pppd 2.4.7 started by root, uid 0
Aug 12 14:46:17 bard chat[20318]: abort on (BUSY)
Aug 12 14:46:17 bard chat[20318]: abort on (NO CARRIER)
Aug 12 14:46:17 bard chat[20318]: abort on (ERROR)
Aug 12 14:46:17 bard chat[20318]: report (CONNECT)
Aug 12 14:46:17 bard chat[20318]: timeout set to 10 seconds
Aug 12 14:46:17 bard chat[20318]: send (AT&F^M)
Aug 12 14:46:17 bard chat[20318]: expect (OK)
Aug 12 14:46:17 bard chat[20318]: AT&F^M^M
Aug 12 14:46:17 bard chat[20318]: OK
Aug 12 14:46:17 bard chat[20318]: – got it
Aug 12 14:46:17 bard chat[20318]: send (ATE1^M)
Aug 12 14:46:17 bard chat[20318]: expect (OK)
Aug 12 14:46:17 bard chat[20318]: ^M
Aug 12 14:46:17 bard chat[20318]: ATE1^M^M
Aug 12 14:46:17 bard chat[20318]: OK
Aug 12 14:46:17 bard chat[20318]: – got it
Aug 12 14:46:17 bard chat[20318]: send (AT+CGDCONT=1,“IP”,“three.co.uk”^M)
Aug 12 14:46:18 bard chat[20318]: timeout set to 30 seconds
Aug 12 14:46:18 bard chat[20318]: expect (OK)
Aug 12 14:46:18 bard chat[20318]: ^M
Aug 12 14:46:18 bard chat[20318]: AT+CGDCONT=1,“IP”,“three.co.uk”^M^M
Aug 12 14:46:18 bard chat[20318]: OK
Aug 12 14:46:18 bard chat[20318]: – got it
Aug 12 14:46:18 bard chat[20318]: send (ATD991#^M)
Aug 12 14:46:18 bard chat[20318]: expect (CONNECT)
Aug 12 14:46:18 bard chat[20318]: ^M
Aug 12 14:46:18 bard chat[20318]: ATD99**1#^M^M
Aug 12 14:46:18 bard chat[20318]: CONNECT
Aug 12 14:46:18 bard chat[20318]: – got it
Aug 12 14:46:18 bard chat[20318]: send ( ^M)
Aug 12 14:46:18 bard pppd[20315]: Serial connection established.
Aug 12 15:46:18 bard kernel: [ 585.839378] 3g-lte: renamed from ppp0
Aug 12 14:46:18 bard pppd[20315]: Renamed interface ppp0 to 3g-lte
Aug 12 14:46:18 bard pppd[20315]: Using interface 3g-lte
Aug 12 14:46:18 bard pppd[20315]: Connect: 3g-lte <–> /dev/ttyUSB2
Aug 12 14:46:19 bard pppd[20315]: Modem hangup
Aug 12 14:46:19 bard pppd[20315]: Connection terminated.
Aug 12 14:46:20 bard pppd[20315]: Exit.
Aug 12 14:46:20 bard netifd: Interface ‘lte’ is now down
Aug 12 14:46:20 bard netifd: Interface ‘lte’ is setting up now
Aug 12 14:46:22 bard netifd: lte (20577): ppp: warning: Sleeping for ‘10’ seconds
I dread to think how many hours I’ve spent on this issue. Hey, I’m a performer, not an IT professional 