I don't think there are problems in that model. If you find a good one low hours I would jump on it. That's what I was looking for when I found a good low hours B2620. They are the same tractor except 3 HP difference. Mine has been a good one.
The B2x20 series are confident machines. Very few to no problems. The LA364 loader works very well also. If using the loader to full rated capacity, a rear weight box/ballast box is needed.
My guess is someone that wanted the higher HP of the B2920 series didn't get a big enough tractor and moved up in size. I love my B2620 and have not heard of any lemon law type issuses withe the three modern B series's (23/26/29hp)
In my case, the B2620 had only 115 hours and the previous owner decided not to build and move to the country and also sold his land. People change plans.
Mine had 26 hours when I bought it, now between 150 and 160. It is an excellent machine for its size. Very well balanced. I plan on doing a 150 hr write-up for TBN with some pictures and thoughts.
I traded mine in at about 135 hours for a bigger L3200. The B2920 was flawless the whole time. Once and a while I do miss it. Lot more nimble than the L is.
Loved my B2620, traded it. In with close to 600 hours on it. Never had any engine problems and ran like a top. Mowed great and did everything I asked of it. I miss it at times, my MX is a lot bigger and I have to get used to it. Would no think twice about getting a B series tractor, they are a great machine and worth the upgrade over a BX.