Can you help me debug this? What other mods were you doing, and what was going on at the time this happened (can you retrace the steps). Do you think another mod is conflicting?
It should work on servers. Let me know!
Is this with the newest version? So you are setting starting hearts to 3 and this happens? I'll look into it.
Getting a heart how? Through exp levels or heart containers? You shouldn't get any invincibility frames. How long does the invincibility last, so I can see if I can notice it? (I have not so far)