Cheers, my Lord of Mesh. Yeah, I checked for more auths but that wasn't the problem, as the standalone version is working alright.
The actual problem was GarageBand apparently. Reason for using GarageBand is this tiny little MacBook I'm now using, tiny indeed, but also severely limited processor-wise. It's a so-called CoreM (even without a fan) and that's OK for walking, not for running or jumping.
So that's why I thought GarageBand would be best.
In the meantime, I have to say, IK Support already responded. That's fast, within 30 mins.
Yet the response is a workaround, as the problem is subsistent ever since GB 10 was released more than a year ago.
Edit: gotta get me some Cosmos