That is odd, do you have any other mod installed other than Procedural Parts? When I added 1.12 compatability I tested it in a minimal install and everything seemed fine.
It should work on KSP 1.12.2, see this comment by NathanKell:
As noted in the posts just above, the current version is not marked as compatible with KSP 1.12.2 on CKAN, but that is being fixed in the next release.