I checked the latest changes with StatList, I have bad news

[Araksson]

The errors remain exactly the same.

This was added that LoadItemStatCost does not read the OPs 0/8/9/10/11 that correspond to the same OPs that fail with the STATLIST_UpdateUnitNewStat function and STATLIST_InsertStatModOrFail

(As a side note, LoadISC from the pre-bulk changes version worked fine (it's the one I'm using))

Sorry for my slowness, I still haven't finished rearranging all my code, it's very long and I didn't check even half of the D2Moo functions (corresponding to ItemsFunctions, DRLG, Path and Missiles).
The good news is that I have made several fixes to the Path and Skills functions to make them work much better (and in some cases, to work directly).

And with Statlist I can't fix those errors.

I also don't have enough time to repair all the maximum details, but I would like to get it since it is very useful to handle all the statlists to try to expand them a bit with some custom code (in addition to expanding the ISC OPs which are also very useful)

[Lectem]

It seems the issue is related to 0x6FDB64A0 (what you call STATLIST_UpdateUnitNewStat).

The other functions look fine to me
Using an amulet with both STATLIST_InsertStatModOrFail and LoadItemStatCost:

On a character with base stats:

Yields

However when using STATLIST_UpdateUnitNewStat it indeed give me something wrong (without even using the amulet!)

I'll investigate.

[Lectem]

I think #28 fixed this, feel free to reopen if issues remain.