With the Info that it is related to the clutter i found a way to fix it. Thanks for that.
It seems to be related with the Config entry

clutterDist = xx;

On both the testmap and our own map we had a custom value (300 on our own map and 512 on HorribleGoat´s testmap).
The A3 Maps using a value of 90.
With this value both custom maps are working again.