I had a 2620 with the 54" mmm. It just dropped to the ground one day while mowing. My dealer sent the cam to me, that adjusts the mowing height, and I replaced it. That did not fix the problem.
I then took the 2620 to the dealer and let him fix it. They fixed and it stayed fixed until I sold it.
I had a BX25 that I cut a lot of grass with and it had a mmm. I never had a problem with the mmm.
I think the set up on the b2620 is a bad idea.
There is too much weight on that cam and it did not hold up for me.:2cents: