DNN edit mode fails after upgrading 2sxc to 17.9 / 18.6.1 (TypeLoadException in ToSic.Eav.Core)

I have a DNN installation (version 9.11.2). After upgrading 2sxc from 17.8 to 17.9 and later to 18.6.1, the edit mode no longer works. Instead, I immediately get an error in the logs

System.TypeInitializationException: 
  DotNetNuke.ExtensionPoints.ExtensionPointManager
---> System.TypeLoadException: 
  Could not load type ToSic.Eav.Documentation.PublicApi 
  from assembly ToSic.Eav.Core, Version=17.9.0.0

Expected behavior: The edit mode should open normally so I can edit content.

Actual behavior: The edit mode crashes right away with the error above.

What I’ve tried so far:

• Redeployed assemblies (cleared the bin folder and copied fresh DLLs).

• Checked for leftover versions of ToSic.Eav.Core.dll.

• Cleared cache and restarted the site.

Question: What causes this TypeLoadException after upgrading 2sxc, and how can I fix it so that edit mode works again?

Just for reference, I had some contact with 2sxc and they said it was an old dll which was still in the bin folder. So it looks like this was not deleted after and upgrade. In my case I had to delete the ToSic.EAV.Tokens.dll file from the bin folder and then everything worked again.