It's a very common problem, widely discussed on different forums. The nowadays cars are more computers than only mechanical machines. They contain several electronic modules which are very sensitive to voltage variations. Looking at the screenshot the Qubo has 9 of them.
My Ducato's BCM looks like that stripped:
Other ones might be even more packed (the airbag module, ECU, ...)
In the Ducato owners' handbook there is a procedure on how to disconnect the battery. Some specialist even say that after disconnecting the battery and before disconnecting the modules lights or other electric equipment (preferably connected to the module to be disconnected) should be switched on / off a couple of times or for some time to get rid of the parasitic voltage and voltage in the capacitors.
Apparently the airbag module can be repaired in most of the cases. There are two companies in the UK, one has better opinions than the others. If interested, you should be able to find it quickly on the forum. Planning to add a passenger airbag in my Ducato I've also found a guy in Poland that says he could repair such errors (and reprogram the module), but I have no experience nor other feedback on his services.
I think that such services should be available also in Austria, Germany or Czechia
You should try to search on the internet.
I'd of course try disconnecting the module AFTER disconnecting the battery and let it like that for some time, but having read lots of threads I know that usually it won't help
