Riddle me this

Riddle me this: how is it possible, that my android plugins ( chartboost/applovin/rate app) work in my test project, then, when exported to my main project - prior to which I deleted any plugin-related folders, including any "resolver" folders, and built, I now get nullrefrenceexception errors regarding android libraries when running it on my test device, even the test scene I used in my original test project.
Then, as a bonus, if I export that entire project back into the test project, it now magically works!
how?????

 

Ok, I'm getting to the bottom of this: after copying the ProjectSettings folder from the original project to the test project, the nullrefrence exceptions have resumed when calling plugins on the android device.

My first thought was that it has to be related to Packages in the package manager, but I compared them in "my registries" and also in "Packages" in the project hirearchy and it's the same.

please help, as I have 70+ projects to update and this will be vital in speeding everything up