On my RT-AX56U, I've been seeing this warning for over a year, regardless of whether the stock or Merlin firmware is installed (for example,
here is my post for 386.4, and
here is another one). It is indeed caused by Adaptive QOS and usually appears exactly one hour later after a certain client that causes it (for some unknown reason) disconnects. For example, in my case, now it does not appear after smartphones disconnect, but as soon as I shut down my laptop, exactly one hour later this appears in the log. So, in your case, I'm almost sure that some client disconnected from WiFi at approx. 9:40.
Some users of RT-AX86U and RT-AX82U also reported that they get this message. There was one report on the ROG forum, and technical support from ASUS told the user that this message can be ignored (however, I'm not sure that it does not affect QOS in the long term).
BTW, it does not look like a crash, it more looks like a warning that some third-party module is re-loaded (based on the
Comm: tc Tainted: P O message).