Here is Martin's response to the solution:
Thanks for that interesting feedback. I can't think of anything that would make the new ASCOM-Driver behave like that. It's not using ActiveX, so this must be something that is coming from APCC.
Maybe it's the fact that the driver has a different name that is causing this issue....
Anyways, happy to hear that it works as expected.
Any chance APCC can take a look at that possible driver name change issue? Here's hoping!