auto trans not shifting on 1990 Audi 200

auto trans not shifting out of 2nd most of the time. Occasionally it does until you come to a stop and it may not again for days. Trans oils and filter was clean. No obvious air leaks.

Asked by for the 1990 Audi 200
Internal leaks around the ATF pump rings , accumulator piston or the apply piston for the direct/reverse clutch all contribute to this.
A function of wear/age.
The good news is it is a fairly simple transmission , any automatic transmission specialist can go through it