I think you should be compensated for the first bet you made that was unable to be 'undone' due to the button not working.
After you realized you couldn't undo bets you decided to continue playing. If you won, they would've paid you. But you lost.
When you made 5 more deposits, did you really believe they would just give you your money back if you lost since the 'undo bet' button wasn't working?
Any casino willing to refund a player in a situation like this would go broke very quickly.