Replacing dotnet core binary with private

How do I replace a dotnet core binary with a private build of the same binary?

I have an application (that I own all the source code to) and I want to replace just a single dll with once that has a fix. Whenever I replace the binary I get the exception

Unhandled exception. System.IO.FileLoadException: Could not load file or assembly '<my dll>, Version=2020.3.1.0, Culture=neutral, PublicKeyToken=null'.
The located assembly's manifest definition does not match the assembly reference. (0x80131040)

File name: '<my dll>, Version=2020.3.1.0, Culture=neutral, PublicKeyToken=null'

at <call stack>

I've tried calling gacutil.exe -i but it didn't work.