Audi TT: Can't code central locking control unit. Help

Hello.
I'm currently experiencing the following problem with a 1999 Audi TT:

The safe could no longer be opened using the remote controls.
The friendly technician then replaced the batteries and tried to reprogram the keys. This didn't work with the great tester, and they wanted to install a new control unit right away.
It turned out to be too expensive, and then they asked me for help.

Then I tried to program the keys using VAG-Com, but that didn't work either.
The error memory was empty except for one error related to the interior monitoring system.

I noticed that in measurement block 6, four keys are displayed, which is quite strange.

The control unit is coded with the value 000000.

When I tried to recode the REP/instruction, it didn't store the new value I entered, but instead saved something completely different. So, it didn't store the value I actually typed in.

I then, as a test, deleted the learned keys (locked 5 times).
The manual pairing process worked. Both keys are functioning correctly.

Unfortunately, due to my modification, the car has forgotten how to blink its lights when opening and closing. Otherwise, everything is working fine.

Does anyone have a tip for me?

Best regards.
Tobi.