read the changelog please...
it says you have to do a clean install of you upgrade from v8.0 interface version...
in this case the problem is that you did NOT deleted your "plugins" folder before you unpacked the new "plugins" from the .zip file
in fact, based on the log I think you didn't even unpacked the zip file properly otherwise InventoryAndStashPlugin.cs and HoveredItemInfoPlugin.cs would be overwritten...