The threads on the wheel hubs looked pretty stripped to me; I saw the wheels just spinning on the gearbox shafts at times.

Perhaps rather than a 5mm baseplate, some vertical ali plates or L sections would be better - it seemed that the bot was flexing after impacts and then the frame was scraping on the floor.

If you use threaded inserts (a good idea IMHO), make them as deep as possible to prevent pull-out.