Bluetooth working but not connecting

Hi Reader,
I am facing a strange problem:
I am able to search devices and find them in the Bluetooth Menu.
I am also able to find my MIB1 Skoda Columbus (Firmware 411) as well. If i change its Name, i see it as well in the Results on my phone*.
But, i am unable to connect. Neither from my phone to the Radio or the other way round.
It is not the original equipped radio for this car, i installed it around 5 years ago.
A while ago i had problems to open Bluetooth/Phone Menu at all.
I gave it to repair and it worked fine for about 2 years. 
I think, it is just a software problem, as i can see and search devices from the Menu.
The usual procedures (Restart, Reset etc. have all been done)

Is there anybody with an idea or maybe even an Update?
What might help: in the FEC/SWaP Menu is only Code 0210004a which says "invalid".

*tested with up to date Apple and Android devices

Thank you for reading so far.

Edited 3 January, 20233 yr by OnTourWithGerrit