Locking/closing cylinder rear door defective

Hello all, I had about half a year ago the problem that the door lock of the left rear door was defective. Reason was a (small, white) broken plastic lever. In the workshop the complete locking cylinder was changed for ~300 €. Today I had to find that now the right rear door also no longer closes. The central locking closes the three remaining doors (visible at the “button” of the doors), only at this door moves the “button” The deadlock also clacks after a short time. If you put the key a bit away (so that the keyless does not address) and pulls on the door handle of the said door, the door starts up and the alarm system. Same behavior as then on the left side. In order not to give Hinz and Kunz access to the car, I now (as before) have to manually press the “button” and then first the central locking. And that every time, because: The central locking is necessary. Is it a common problem for me to open the door again? 🙁 Now my question to the community: Is this a common problem? Is there perhaps a cheaper hack to replace than the complete lock cylinder? Thank you and greeting – MedanoCC