I got to the end of the run and hit tyrant with the rocket, however the only thing that loaded was the animation of him getting hit and I lost the entire run. Anyone else had this?

GrowthKasei had this happen on Claire A and he thinks this happens if you skip the cutscene too fast.

Ah that makes sense. Was a damn shame though. I was on a 1:14 run so it was very disappointing

Yes. For G4, if you skip the cutscene way too fast, the screen will be frozen in place but you can sometimes see the subtitles of what should be playing pop up. No sound though.