What happens with over 4 OTA network ports?

I have a strange behaviour with my latest Arduino IDE:

As soon as I get more than 4 OTA network ports active in my WLAN, the Arduino IDE 1.8.12 begins to display only the three oldest...

The devicess are all correctly logged into the WLAN and operate as they should, with distinct MAC and IP addresses. They are just not displayed any more on the IDE and i can't program my devices anyore...

Has someone noticed the same behaviour, or have a solution?