Small update: If you boot into Safe Mode, KiXforms 2.47.5 works without issue.
So it seems to be some kind of DEP (Data Execution Prevention) that got added in the Creators Update.
I've completely disabled Windows Defender, Smart Screen etc. but the problem still exists in "Normal Mode".
I've even freshly installed a laptop with the Creators Update ISO to make sure it wasn't the 'Upgrade' process that caused the problem.

Now the good news: Shawn is working on a version that has a workaround for the problem and it seems to work.