1. Check these things, it's probably one of them that's causing the problem:
-Check that GPxSet is enabled in GPxPatch.
-gpxset.ini file in GPxPatch folder links to correct performance files.
-2001 Levels selected in GP4 Race Options menu for performance levels.
2. That means there is likely a problem with your anim.wad. Try creating the wad with GP4 Master or WadUpdater instead of EasyWad.
X (@ed24f1)