Unless those other mods deal specifically with reinforcements, they won't touch the AdventGlobal list.

Thing is, if it touches the reinforcements and is not an enemy mod, then deleting those lines from their missions.ini is likely breaking that mod. So those mods are straight up incompatible, like for example the Reinforcements Extended mod.

I'm still looking for the mod that's breaking my reinforcements. I have some 70 mods in total, so it's annoying but not impossible.

Have you seen that i listed the enemy mods here:
https://steamhost.cn/steamcommunity_com/workshop/filedetails/discussion/793861140/282992646972923662/
telling you which ones need an edit and which ones don't?

Got it! I still had the Advent Psi operative installed. (Or 628352640 as it's descriptive mod name is in the steam workshop directory)
I must have overlooked that several times in my subscribed list in steam. I thought I only had the LW Alien pack...
Will still have to check, but it's listed as needing an edit, which I just did, so I am confident that fixed the issue.
Thanks for the help!