Nice work. I implemented schedules, tasks, sequencing quite a few years ago (Geometry Gym: Navisworks 4D IFC), but I’m not sure our files have ever been validated in detail across other implementations. Here’s an ifc2x3 file to test against (generated a couple of years ago). More than happy to discuss if you find it not compliant or needs improvements.
180905tower4difc2x3.ifczip (98.6 KB)