I tried changing the channel to auto as suggested here but that didn’t do the trick for me.
Found out that running a speedtest (on the ookla website) does trigger the fault though.
Funny thing.. first time I did the speedtest both 2.4GHz & 5GHz went out.. so had to do a hard reboot then. The only thing different was that transmission power for the 2.4GHz radio was set to medium, instead of max. It’s on max now again and when I do the speedtest only the 2.4GHz radio drops out.
Downloaded a troubleshoot file so if you want it, it’s here.