Venturer dvd player resetting every time you...

I have a car cd player that attaches to headrest. One of them has started to reset itself back to main menu everytime we hit a bump while driving. Called manufactor help desk they say that i need a firmware upgrade. Went to there website to get the upgrade and it is not avaliable for my model number. I was kind of questioning there firmware upgrade because she said that it must of just been set wrong at the manufactor but if that were the case why has it worked great for the last year and just started to have problems? Please help!