vb.net Postgressql - .net app runs fine on devl vm but when running on a client machine have DLL error

I have a vb.net app which runs fine on the developer machine but when running it from the client machine with PGSQL (v12) installed, I get this dll error when performing a connection to the local machine server from the app itself.

postgresql Could not load file or assembly 'System.Runtime.CompilerServices.Unsafe, Version=4.0.4.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

The DLL is references in the vb.net executable and I can confirm the DLL has been copied to the client app directory - I did not "install" it there as such, but a literal file copy as I have my app set up so it will run off-the-cuff, the only installations I have had to do, was with the VS C++ libraries and RDLC report setup. I'd rather not do an uninstall of the app from the client but am happy to install a different app if it gets that running

I cannot find anything on the internet that is indicating what is wrong other than the above.

Thanks