I don't really think there's an explanation that won't still leave it feeling wrong (besides, maybe, "That wasn't actually Jason- it was Everman/a doppelganger from another universe/his evil twin/really I don't care what the fuck it was so long as it wasn't actually Jason"). But yeah, there are a variety of factors that a half-decent writer could put together to make it in-character enough that the damage can be repaired.