Dear all,
I have got exactly the same problem on two totally different
computers, both running Lubuntu 20.04. I have found this bug
report as one of the very few search results for the obviously
very rare error message:
wlp1s0: disassociated from xx:xx:xx:xx:xx:xx (Reason:
33=DISASSOC_QAP_NO_BANDWIDTH)
journalctl -f shows this immediately as soon as the wifi
connection gets lost.
In my case the problem came with an update to kernel 5.4.0-58. Going back to 5.4.0-56 or 5.4.0-54 resolves the issue.
I have a similarity to Jürgen: I am also running a Fritzbox with
a repeater - in my case in a Mesh environment, so everything
(router, repeater, 2.4GHz, 5GHz) has the same SSID.
I hope this helps to narrow down that issue.
Rgs,
Martin