The 722.109 trans had an adjustable reverse band. It also had a servo piston that commonly broke or needed resealing. None of these problems should occur to a year old rebuild, but sh** happens.
Take it to Donnie or other competent shop if he is too busy. Take it too someone who can deal with incar repairs (many only exchange transmissions)
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician