btw /sys/kernel/debug/crashlog was empty. ( Source: Crashlog retrieval (MIPS) - #3 by hailfinger )
I've now hit a different log line for a PC associated with the AP:
[934478.437766] Rekeying PTK for STA ac:7b:a1:xx:yy:zz but driver can't safely do that.
What does that mean? Any negative consequences to be expected after that occured?