Eternal Youth Life Recovery not healing fully on Predictive Mode

I'm using Eternal Youth and Blood Magic and reserving almost all my life.
I should have exactly 120 life unreserved to cast my main skill - currently Arc at 98 life cost. Eternal Youth should heal my life pretty much instantly back to 120. However, if I spam cast my skill sometimes it gets stuck below that number and i cant cast me skill again.

This seems to be connected to the networking mode. I could only reproduce this behavior on predictive mode.

Here is a gif of it happening:

https://imgur.com/a/ruvaGbf


EDIT: I'm using Zealot's Oath too which might be relevant.