Migrating a project from 5.6 > Unity 2018.3 (lol) I got through most of the pains, but quite frequently now I get presented with the "API Update Required" popup. (the one where you choose "No Thanks" or "I made a Backup. Go Ahead!") It seems that If I click "I Made a backup. Go Ahead!", Unity starts spamming Exceptions from ScriptCompilerBase and never seems to finish compiling. If I select "No Thanks", compilation finishes, there are no errors, and I'm allowed to run the game. Any idea what might be going on here?