Tested on version 1.2.7.2
This mod is very cool and I would like to play with it without the following bugs.

• At death, there is a chance that skills will be reset, but when I re-entering the world, they will return again.
• At death, if the skill of additional health is upgraded, this hp disappears, and in order to return it, you must upgrade or downgrade this skill.
• To reduce the skill level, you need to have as much experience as you need to upgrade it. I think it's wrong and it needs to make it possible to downgrade skill even if you do not have experience.
• If you upgrade Athleticism skill, being at the bottom of the reservoir and moving sideways, you will randomly quickly move in different directions.
• Feather Fall skill does not give the effect of upgrade. 0% is always written.
• There is no description and icon for the skill of additional health.
  I suggest a name: Additional Health
  Description: Give %f additional health points.
  Image: https://postimg.cc/Hjp84kD6

"At death, there is a chance that skills will be reset"
I cannot reproduce this in my clean environment, many reports but Forge's SimpleImpl works just as fine as other mod
Check if any mod cancelled PlayerDeathEvent or something takes control of health system
If this still happens, I will consider synchronizing all stats in a regular time

I believe Athleticism shall be working correctly in 1.13

Other bugs will be fixed.

@NanamiArihara Actually, I got "death reset" problem too. Many people in Chinese forum also feedback this problem. But what I encountered was not really reset, it just displayed as 0, the real level did not change. Though I need downgrade it to made it right.

where can I get my personal NBT data?
@NanamiArihara and what time of the NBT do you want?

I found a complement of this issue, if the skill is not at highest level, and I died, I need cost xp(the amount is level 0 to level 1) to left click the skill to make it show the right level. Previous message just showed what it performs at highest level. (not like issue#43 says, every time I die it comes. Re-enter the world could not solve it)