Front deck adjustment on a Toro Time Master

I have a problem with my Toro Time Master Walk behind keeping the front end adjustment in place. It drops to the bottom as you mow.

Has anybody else had this problem?

I have not disassembled it yet to try to figure out what is going on.

Anybody running one with the same issue please give me input as to what you did to reconcile this problem.

Thanks.

Front deck adjustment on a Toro Time Master