Hello

I have had this router approx a year now and previous RB4011 worked ok with the same setup.
ZTE MC801AHW 5G router is in brigde mode and RB5009UG+S+ is the firewall and router.
Problem is that approx after 30 days internet disconnects this way:
Mikrotik cannot find dhcp address says only searching when trying to release or renew.
Ethernet port is UP disabling or enabling does not help.
Internet detection turned off.
ZTE is not answering to the ping. ZTE reboot does not help.
In the logs this is only thing: radvd received Router Solicitation packet with invalid code=242

Only help comes when i reboot the mikrotik and everything is fine after that.

What could be wrong?