Ok, landed a fixed version. The fix is a bit weird, but I think it should not cause issues - I have essentially dropped all migration-related code.
The reasoning is that the migration code was all relevant only for mod versions written for Factorio 0.17 and below, and Factorio 1.1 cannot load those savegames at all - so you would have to upgrade via Factorio 1.0 and install Pavement Drive Assist for 0.18 first, which will then apply all the relevant migrations.
So kinda a nice way to get rid of some of the unused code. Still, do let me know if anything broke with this, and thanks for reporting the issue :)