I HAVE PROBLEM ASSOCIATED WITH ROLLER MISSING OF REVERSE GEAR BEARING WHILE ASSEMBLY WITH SHAFT IN TRANX-AXLE?

WHILE ASSEMBLY OF COUNTER SHAFT AND INPUT SHAFT REVERSE GEAR BEARING IS USED.BUT IN SOME CASES FOUND THAT ROLLER IN REVERSE GEAR BEARING IS MISSING. AND IT IS ASSEMBLED AS IT IS.
I WABT TO DESIGN SOME POKA YOKE SUCH THAT BEARING CAN NOT BE PLACED IF ONE OF THE ROLLER IS NOT PRESENT. OR SOME POKA YOKE TO CHECK THE BEARING BEFOUR ASSEMBLY AND IT SHOULD CHECK ALL THE ROLLER AND IF ONE OR MORE ROLLER IS NOT PRESENT IT WILL SHOW SOME INDICATION OR ALARM.

Please don't SHOUT.