No, the windowlist is also implemented like in CORE and is not being deleted.
Since I log all scripts in the console I am able to see the sequence of function calls:
[10/20/2020 5:52:13 PM] ct/scripts/ct.lua, toggleEffects, Ende
[10/20/2020 5:52:26 PM] ct/scripts/ct_entry.lua, onMenuSelection
[10/20/2020 5:52:26 PM] ct/scripts/ct_entry.lua, delete
1st entry: toggling the effects to have a larger ct_entry to click on for deletion - note the time difference to the next entry - 13 seconds!
2nd step: open the radial menu and select the menu-item for deletion
3rd step: deletion is triggered with the already posted sequence of steps before...
there must be some kind of memory mis-management since it believes that an object is missing that is actually there ...
I really appreciate you trying to help and I wish your guess was right because the problem would already be solved then. Unfortunately, it does not seem to be so simple.