A fairly common cause of this sort of problem is badly fitted reed blocks. They need to be a snug fit at both ends, and not have any warp on the base board so there is a good fit along the full length of the block, and with the vents in th blocks well aligned with the holes in the base board. Warped base boards are not uncommon on older Hohners.You may well have just found the problem. I'll check. Thanks.
And believe me, the man who tuned it, knows what he does. I'm just looking for a bigger sound that's all.
If your man is on top of his game he should have noticed this type of problem.