I am unfamiliar with the 'Grocery Store Bug'. Remove the harvester (if you can), and your sim will resume using other means of transit.
I believe the 'Grocery Store Bug" being referred to is where you couldn't buy/sell at the grocery store if you had special seeds in your inventory. So far I have not seen an issue with having the harvester in the inventory, next time I'm playing, I'll pay closer attention to what transport those sims use.