Not sure if anyone else has discovered this but i havn't found any discussion showing why

Do not use more then 255 skill points
The reason for this is the game loads all the sp you used on a stat onto a max 256 value integar
That includes a 0 and 0 stands for default Tamed Stat value + 255 sp you use = 256
When you go beyond the value it resets the value Back to 0 continues from there
So useing 256 SP would essentaially be 0 Sp used and spending 257 would be 1 Sp used etc will continue till you go beyond that integer max again

It only effects the given stat so you can use 255 sp in hp and 255 in melee and no problems
If you use 255 sp in hp an 256 in melee it will only be the Melee to be as if it reset

Also you can spend as much as you want into a stat while in game it only does this on reload

The only workaround i can think of to the limitation is to use a dino mindwipe mod to give you back all the Skill points you used and then reuse them while in game
I do belive this just a limit and not really a bug as vanilla Ark you would never even experience this reset