Delete repository objects from non existent namespace

[#1]

Hi,

we have old 3rd party software on our system that we no longer use and want to remove. The software producer was not able to provide assistance so I'm trying to remove it manually. 

The problem I'm facing now is, the software seems to be in an obscure namespace that is not present on the system and that cannot be created either.

When I try to delete an object in the following package I get an error:

When I try to add the namespace in transaction SE03 I get a warning at first followed by an error:

Via debugging I found out, that the valid key range needs to be a "/" followed by a letter.

Can anybody provide an inside into how to best proceed here?

A last ditch effort might be to change the namespace of the package in table TDEVC but that seems risky and I have no idea if it would even work.

Kind regards,
Christian