I just stumbled upon a combination of "errors" I never saw before when I tried to create a new replica from Server A on Server B (running locally here on my machine):

Thanks for this info, Notes buddy.

Directly following the next cryptic message:

Okay, let's check the directory permissions (this is a Linux based machine) - all good so far. I also can create new databases and create replicas of others, too. So what the hell?

When I tried to create a new database using the same name as the original replica on Server A, I got this:

Same message but nonsense at all, as this is a file and not a directory.

The reason

It turned out that there already was a database with this exact filename. Notes, if so, then please just tell me that! 

For the record: 12.0.1FP1

12hclnotesquicktipwtf