Gateway IPv4 sometimes not reachable, don´t come up

[Bytechanger]

Hi,

My OPNSense WAN is connected to on an "Deutsche Glasfaser" modem.
I´ve two gateways, one for IPv6 and one for IPv4.
Every day my ipv4 Gateway goes offline (Monitor) and doesn´t come up.
When I push "reload" on Interfaces->Overview->reload it comes up.

Where can I see (logs etc.) where is the fault?

Greets

Byte