Router reboot problem

[HenrysCat]

I have a TP-Link VDSL modem 192.168.1.1 connected to my opnsense box 192.168.0.1 that is connected to my network, everything works perfect, port forwarding etc until the internet drops which happens a lot here.

Once the internet is back up port forwarding no longer works, I can see the connection in the firewall log, port 1194 for my VPN for example, but the VPN never connects, same for other services running on 443, 80 etc
If I reboot opnsense all starts working again.

Any ideas?
Thanks all