Recently bought a 1999 A4 1.8T Quattro, previous owner told me that the transmission shifts roughly and would not go into 5th gear. The previous owner also stated that transmission was not the stock one and was from a B6, can not confirm the validity of this as I have no idea what the difference is. I have been driving it for about 3 months now and noticed that once it shifts into the 4th it will not shift back down into any lower gear unless put in park and turned off. This has become an issue because the acceleration is extremely slow, putting me in dangerous situations when trying to make turns or just accelerate in general. Ran a check on the codes and received these codes back. If anyone has any advice for what this means or what I can do to fix this it would be greatly appreciated.

This is the TCU unit and the number

MIL code

No Speed Sensor

TCU code, which had no code or WSC