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.

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1 answer
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