@Raphael303 

I have started the AP, then unplugged the modem. Cleared the log. Plugged in the modem, refreshed the log after a while
The log text file won't upload. So here it is in plain:

2024-06-06 07:49:32 [5] Httpd: Clear log.
2024-06-06 07:49:42 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=remove
2024-06-06 07:49:42 [6] 3G: Hotplug: 12d1_155e_123456789ABCD, not the used switched_3g device.
2024-06-06 07:50:06 [6] 3G: Hotplug: id[0]=12d1_1f01_123456789ABCD, class[0]=unswitched_3g, action[0]=add
2024-06-06 07:50:09 [6] 3G: 3G/4G Modem vendorID: 0x12d1; productID: 0x1f01
2024-06-06 07:50:09 [6] 3G: init E3372h-320(0x12d1-0x1f01)
2024-06-06 07:50:23 [6] 3G: 396: go to already_switched.
2024-06-06 07:50:24 [6] 3G: 525 File: /var/3G/12d1_1f01_0
2024-06-06 07:50:26 [6] 3G: 830: The modem name of the global parameter is ETHER_MODEM.
2024-06-06 07:50:27 [6] 3G: 956: This is one LTE modem which has no tty interface!
2024-06-06 07:50:39 [5] DHCPC: Recv OFFER from server 192.168.8.1 with ip 192.168.8.102
2024-06-06 07:50:40 [5] DHCPC: Send REQUEST to server 192.168.8.1 with request ip 192.168.8.102
2024-06-06 07:50:40 [5] DHCPC: Recv ACK from server 192.168.8.1 with ip 192.168.8.102 lease time 86400
2024-06-06 07:50:40 [5] DHCPC: Recv DNS server address 192.168.8.1,0,0,0,0
2024-06-06 07:50:43 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=remove
2024-06-06 07:50:45 [6] 3G: 3G/4G modem is plugged out.
2024-06-06 07:50:45 [6] DHCPC: Unicasting a release of 192.168.8.102 to 192.168.8.1
2024-06-06 07:51:03 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=add
2024-06-06 07:51:06 [6] 3G: 3G/4G Modem vendorID: 0x12d1; productID: 0x155e
2024-06-06 07:51:06 [6] 3G: init E3372h-320(0x12d1-0x155e)
2024-06-06 07:51:17 [6] 3G: 274: go to already_switched.
2024-06-06 07:51:18 [6] 3G: 525 File: 
2024-06-06 07:51:20 [6] 3G: 830: The modem name of the global parameter is ETHER_MODEM.
2024-06-06 07:51:22 [6] 3G: 956: This is one LTE modem which has no tty interface!
2024-06-06 07:51:23 [5] DHCPC: Recv OFFER from server 192.168.8.1 with ip 192.168.8.102
2024-06-06 07:51:24 [5] DHCPC: Send REQUEST to server 192.168.8.1 with request ip 192.168.8.102
2024-06-06 07:51:24 [5] DHCPC: Recv ACK from server 192.168.8.1 with ip 192.168.8.102 lease time 86400
2024-06-06 07:51:24 [5] DHCPC: Recv DNS server address 192.168.8.1,0,0,0,0
2024-06-06 07:51:30 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=remove
2024-06-06 07:51:33 [6] 3G: 3G/4G modem is plugged out.
2024-06-06 07:51:33 [6] DHCPC: Unicasting a release of 192.168.8.102 to 192.168.8.1
2024-06-06 07:51:51 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=add
2024-06-06 07:51:54 [6] 3G: 3G/4G Modem vendorID: 0x12d1; productID: 0x155e
2024-06-06 07:51:54 [6] 3G: init E3372h-320(0x12d1-0x155e)
2024-06-06 07:52:05 [6] 3G: 274: go to already_switched.
2024-06-06 07:52:06 [6] 3G: 525 File: 
2024-06-06 07:52:08 [6] 3G: 830: The modem name of the global parameter is ETHER_MODEM.
2024-06-06 07:52:09 [6] 3G: 956: This is one LTE modem which has no tty interface!
2024-06-06 07:52:11 [5] DHCPC: Recv OFFER from server 192.168.8.1 with ip 192.168.8.102
2024-06-06 07:52:12 [5] DHCPC: Send REQUEST to server 192.168.8.1 with request ip 192.168.8.102
2024-06-06 07:52:12 [5] DHCPC: Recv ACK from server 192.168.8.1 with ip 192.168.8.102 lease time 86400
2024-06-06 07:52:12 [5] DHCPC: Recv DNS server address 192.168.8.1,0,0,0,0
2024-06-06 07:52:19 [6] 3G: Hotplug: id[0]=12d1_155e_123456789ABCD, class[0]=switched_3g, action[0]=remove
2024-06-06 07:52:21 [6] 3G: 3G/4G modem is plugged out.
2024-06-06 07:52:21 [6] DHCPC: Unicasting a release of 192.168.8.102 to 192.168.8.1