Unsure if this issue is for here or for the Extended Vanilla Equipment dev, but I was using another quality mod (didnt have any of its new qualities unlocked or in use yet) but it seemed to work fine for me and my friend in multiplayer, when swapping to this mod my friend was no longer able to connect to my game due to desyncing on loading in, if we disabled this mod OR the extended equipment mod then the game would work fine again, the equipment dev says he doesnt touch anything related to qualities so was wondering if you had any idea what could be causing it

What version of quality do you have? I made significant changes in version 1.0.1. So if you started the map with 1.0.0, I recommend finishing the map with this version and not updating until then.
I don't plan on making any major changes now, but the jump between 1.0.0 and 1.0.1 is significant.

We used these 2 mods on this save which worked fine together:

https://mods.factorio.com/mod/Additional-Qualities?from=search
https://mods.factorio.com/mod/Better-Power-Armor-Grid?from=search

We then deleted Additional Qualities and added Version: 1.0.1 of your mod but then we had an instant desync on my friend connecting to the game, we then tried to delete the equipment mod and the game worked fine again, we can use your mod with our other ones fine, but as soon as we re-add the equipment mod we went back to having desync issues, eventhough we have 0 equipment entities on the map at all, which seemed very strange to me that the mods would be incompatible

Better-Power-Armor-Grid - I also use it on MP and it works for me, but I have the 1.0.0 quality version on the map. I'll try MP with version 1.0.2 in my next game.

As I said, I made significant changes in version 1.0.1. The only thing I can think of right now is to try setting a different quality mod (not All with 40 Q, but only the 9-10 Q ones). However, I didn't change anything in the 40 Q mod that would break it, so if you're using that one, I don't think there's a problem with the quality mod.

Another thing I can think of. Try quality version 1.0.2. Load the map in single, save it. And have your friend download version 1.0.2 as well and only then try loading the map for MP. here should be no desync now

Nvm ignore this msg, trying 1.0.2 now

All with 40 Q in 1.0.2 still causing desync, but New with 5 new qualities seems to work fine, think we will just use that one for this save then, maybe just a save issue.

Side issue that ive noticed seems to be: https://i.gyazo.com/b177f72a7f6011324fb96bd8ae9b12d6.png

I hope so. I haven't tried the new version on MP yet, but I can't think of any reason why it would cause a problem. Just try the new map just to test if it will work in MP. If you have the chance.

Otherwise, I fixed the translation bug in 1.0.3.

Started getting desync issues again after a few days, after removing this mod the issues stopped again. I may be completely wrong but I believe some mods in our pack are not working correctly because this mod changes the base game epic/legendary tiers, again its purely a guess but I have no clue what else to try.

I don't know. No one else has this problem or hasn't written to me. Moreover, I personally have played 2 MP games with 40 qualities (140+ mods) and there is no problem connecting others who are playing.

It really looks like you're using some combination of mods that are interfering with it. Maybe another mod that somehow changes the qualities or interferes with them? Maybe even dynamically during games?

It doesn't change the basic qualities, they are fixed by the game. Only the values ​​change and they have no impact on desync. And all of this is a setting when "startup", so every player has it the same and cannot change it during the game.

But if you encounter a problem (combination of mods), let me know and I'll add the unsupported ones to it