Dear Hans,
Thank you very much for your instant answer to the issue and for the suggested workarounds. I added a wrapper method around the del transaction that sends the ID of the object as a parameter and now it is even better.
Thanks for the suggestion about the deletion of the blob files. I will reconsider using this function. Initially it didn't seem a good idea but I am starting to think that it is.
As to the issues that you have put in your previous message I am not sure yet what the right approach should be. I'd trust your judgement.
Regards,