Well, knock on wood, but after last round of config changes my 5G wifi is still working with 10 days of uptime...
[admin@MikroTik] > /system resource print
version: 6.44.5 (long-term)
build-time: Jul/04/2019 10:32:21
[admin@MikroTik] > /interface wireless monitor [find] once
status: running-ap running-ap
channel: 2447/20-Ce/gn(17dBm) 5200/20-eCee/ac/P(20dBm)+5530/80/DP(24dBm)
wireless-protocol: 802.11 802.11
noise-floor: -102dBm -105dBm
overall-tx-ccq: 77% 100%
registered-clients: 2 1
authenticated-clients: 2 1
wmm-enabled: yes yes
I can't suggest too much aside of 6.44.5 but I currently have it set up in 80+80 mode with statically configured frequencies. Specifically
set wlan1 band=5ghz-n/ac channel-width=20/40/80mhz-XXXX frequency=5200 secondary-channel=5530
I do have
(and I remember ANI being a massive pain on OpenWRT in the past) but it was off the whole time before anyway.
I actually had a massive amount of trouble setting up 80+80.
For first bunch of attempts "set secondary-channel=" command was accepted, returned me to prompt... but crashed the wireless subsystem.
Both 2.4 and 5.0 wifi go down, and many commands such like /interface print (not to mention /interface wireless print) just frozen the console.
A minute or two later I've been also losing the ability to open new ssh connections - key was accepted but then terminal hanged in blank.
Only fix for that was a power cycle.
Actually, no, that was a long night and I forgot the whole story.
Because the faulty config was already saved, after a reset I could log in but wifi was still crashed and trying to do e.g. /interface print would freeze the management plane again.
So after that power cycle it was actually required to restore backup, which would then say it will restart but fail to do so (because crashed system components).
Manual power cycle at that point brought me back to the config from backup, so with the ability to edit wireless config again.
So, try another setting, freeze the device again, rinse, repeat.
I'm still not 100% sure but I think what resolved this was setting
Earlier it was specifically
on the assumption of "if I'm setting frequencies manually, I should set up the control channel position manually too, right?".
But... yeah. Works for me for now, at least.
PS. Can anyone point out to me what's the logic for the code-tag to sometimes render inline and sometimes as a box?