PCGs disappear when changed, every actor needs to be moved once (ony by one) to fix.

It seems I Found a Fix/Workaround, just in case anyone will encounter this in the future:

“Actor Filter” needs to be set to “Self”, not “Actor” (which is also the default) - many previous tutorials from pre 5.5 will teach you the wrong setting for this, and it will not work in 5.5+