This might not actually be an issue, but whenever you get the +1 Health through the Defense skill, you lose it upon death.

Able to confirm this, also happens with the /attribute command

Heres the vanilla bug report https://bugs.mojang.com/browse/MC-179940

Ill try to make a patch, which should hopefully automatically update your attributes to what they should be

Oops, forgot to close this, 2.0.3 fixes this issue