In recent firmware releases, interference mode is disabled by default. Maybe that's related.
Can one of you with the issue try running this over telnet, and see if it helps with long-term stability?
Code:
wl -i eth1 interference 4
wl -i eth2 interference 4
This is what used to be the default value in the past according to another user. I know that last few releases had it set to 0. The available options:
Code:
admin@RT-AC66U:/tmp/home/root# wl -h interference
interference
Get/Set interference mitigation mode. Choices are:
0 = none
1 = non wlan
2 = wlan manual
3 = wlan automatic
4 = wlan automatic with noise reduction
Let me know if it helps. If it does, I'll integrate the option into Asuswrt-merlin.
EDIT: Note that this option does not survive reboots, so you have to re-run that command after rebooting the router.