connection to AP still exists, but no more IP traffic possible

[Jami17]

With ESP32-CAM working as STA I have observed several times, that it and the AP report that connection still exists (no SYSTEM_EVENT_STA_DISCONNECTED occured in ESP32-CAM), but no more IP messages can be exchanged. No ping / UDP / HTTP. The ESP32-CAM sits in the basement so signal strength is weak, it reports -77 .. -83dB. But usually IP exchange works quite well. The module sends UDP-msg every 10s during the test phase to a PC, and these also stop arriving.

It all works again after a ESP32 reset or turning the AP off / on.

What can be done to ensure reliable IP connection over long periods?
In the worst case it would connect to 8.8.8.8 once in a while to check if IP is still working. But I would like to avoid that.