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i am in a layer of DLL hell usually reserved for microsoft employees

Based upon the versions it also appears you live in the early 2010s..

.net framework 4.8 yeah. not by choice just seems to be what AudioBand is on

4.2 by your version error... that might be your issue.

The csproj of that project is 4.8 so you should probably be using 4.7.1 of the System.Runtime.CompilerServices, as anything greater than that is .Net 5. Either way its saying that file of that version, doesn't exist.