The only cure I'd seen for flashing odometer was proxy alignment, until I saw this recently:
I have a hack for you! Blinking miles on dashboard fix.
So. my 500e had this issue like a millions of 500 (including the non electric). The miles on the dashboard started blinking. This is (supposedly) because the dashboard lost it power or something related to that. Time, partial miles, etc all was ok, just started blinking. 12v Battery is NEW, not...