We have a lot of problem with Ethernets on routerboards like 411ah 433ah between mikrotik on bridges. The Ethernet look like something is connect to it but there are no traffic at all on it. We disable and enable and sometimes it works sometime it doesn’t, and we need to go where is the AP and reboot it(switch on and off).
I have recently had these problems too. I have a remote client to 6 hours from my place that I had to enable watchdog because I lost the connection with my cisco switch. I tried everything to change the settings on my switch port half, full, 100, 10 and nothing, until you restart the RB411.
I am currently testing a card with the version 5.01 and have not had that problem I have a test week. I think the other cards I will make a downgrade.