Hi Alexander,
thanks very much for your help and detailed explanations. Adding the mappedBy / inversedBy Information without the Doctrine mapping annotations acutally was something I hadn’t tried yet. Still, this led to an exception within Doctrines SqlWalker which I didn’t really want to investigate any further (probably some issue within a query), so I decided to follow your advice and overthink if I really need a bidirectional relation and dropped it.
So basically: problem solved (and yes, it’s a legacy database, but still thanks for the links - it’s always good to reiterate some things from time to time) - and thanks a lot for all the work you obviuosly put into the post. It’s much appreciated!