This means that GMS2 corrupted one of the scripts (GMLive_exec in this case) during import - removing the script and re-importing will fix it. Failing that, rename YYMPs file to be a ZIP, extract it, and copy-paste the code from said GML file by hand.
I added a mechanism to check for missing scripts (and show a slightly more meaningful message), but it doesn’t detect a few of these due to execution order no longer being reliable.