Connection problem for HA App on iOS with Mimo Routers

I have a WiFi 6 network with 3 Asus ZenWiFi XT8 routers.
When walking around with my iPad it switches automatically to the AP with the best reception. Problem occurs when that Access Point is different from the AP to which the HA server is connected.
Then the Home Assistant App is thinking a long time and then ends with NSUrlError -1001.
This seems to me a iPasOS problem, because it only occurs since a few days ago after iOS upgrade.
Before that I did not see this problem. If I force my iPad to connect to the same AP as HA the connection immediately recovers.
Any clue on how to solve this (workaround maybe) or what could be causing it? Thanks for any help!