Break START BAR Key?? Need Help

Hi.

START BAR KEY on my MPC doesn't functions correctly . When I click on END BAR Key the time is go to NEXT seconds but When I click on START BAR Key time doesn't BACK.

This problem is on AKAI and JJ OS so probably this is not BUG??

How repair this thing?? I have MPC on 2 months. What is it??

Anyone has this type problem??

in order to use "Start" and "End" you must press them simultaniusly with "Go to" ... try it out