Running the latest version of ViaRewind on a 1.8 PaperSpigot server. Absorption hearts don't show for either version players.

If even 1.8 players can't see the absorption hearts, the issue won't be 100% on ViaRewind. However there is an issue with absorption hearts. I think this is related to issues in ViaVersion (EntityTracker and/or packet ordering).

The absorption hearts are not shown even for 1.8 players?

@Gerrygames Occasionally, the 1.8 players can see the hearts. Seems to be random but I could try to look into it more.