I have observed network traffic with tcpdump on lan1 while the problem happens and I did not notice anything weird before the lan port goes down.
When the problem arises a gap of 5 seconds happens in the interception of the network traffic, which confirms packets do not go through in that period.
However, I am not connected to lan1, other computers are connected to that port. I am connected to another port which is not showing up in the logs.
I will repeat this test but sniffing traffic on the whole lan bridge and also the port I am connected to to see if I can find anything useful.