connection issue on opnsense after cablemodem change

[Beleggrodion]

I have a strange issue on one of our opnsense firewalls. And i don't know how to correctly set the title for this issue.

Because of an issue with a bad performance on the site the provider changed the old cablemodem to a new one. The modem provides the public ip to the opnsense via dhcp, so the WAN interface is configured as DHCP client (and not changed during the switch of the modem)

Since then the opnsense looses irregular the network connection. ping of the public and ping of the internal ip on the LAN interface are not possible anymore. the provider says they dont see a problem on there side.

Then 2-3 times powercycle the opnsense (its an apu2) and then it looks stable for hours.

I see in the log many entries like this:

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<27>1 2023-10-06T23:29:10+02:00 cust-ch-xyz01-fw01.customer.intra dhclient 60785 - [meta sequenceId="1"] Bogus Host Name option 12: cpe_000db94ae4d4 (cpe_000db94ae4d4)
<13>1 2023-10-06T23:29:10+02:00 cust-ch-xyz01-fw01.customer.intra dhclient 56941 - [meta sequenceId="2"] Creating resolv.conf

but this log entries are already there before we switched to the new cablemodem. So i think this is not the issue? but perhaps there is also a solution to fix this?

This night, the connection was lost again around 02:20 o'clock. the opnsense is uptdating itself around thursday on 02:00 o'clock. the reboot was done around 02:17 o clock and as i look into the  system log and see that the wan interface (igb0) looses his connection and also lan (igb1) and then some scripts are triggered, which causes the loose of connections, and so on?

Because also i see something like:

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<11>1 2023-10-12T02:20:13+02:00 cust-ch-xyz01-fw01.customer.intra opnsense 67423 - [meta sequenceId="71"] /usr/local/etc/rc.linkup: The command '/sbin/ifconfig 'igb1' inet '192.168.123.1'/'24'' returned exit code '1', the output was 'ifconfig: ioctl (SIOCAIFADDR): File exists'

So perhaps some scripts are triggered get stuck?

Currently after a power cycle the opensense come up and then looses his connection and perhaps , some seconds later, it comes back again and is available via network. But it can loos it afterwards again. This morning we needed three

Im currently not at the location and there is no one with a serial cable so view on the console , when connection is lost, is not possible.

The almost complete log of today (until i write this) is attached here.

p.s i changed ip's and so on in the log for privacy.

[cookiemonster]

I think all these are symptoms not the cause of the problem.
option 12 of dhcp is to get the host name from the dhcp response unless you've set a value and is trying to tell the dhcp server (your isp) what the router hostname is. I think it is being ignored.
Creating resolv.conf is more telling. This happens when the interface has a change that triggers the reconfiguration. The trriggers that you see during are normal and what happens to reconfigure after a change.
So my guess is that there is something happening between the isp and modem or modem and WAN. Look back on messages and maybe there are some more indicators.