Torben,
Many years ago I had the same problem when I had to remove the VCR to upgrade the software.
If I remember correctly it is important to hold the video door open while aliening the VCR in place, so the answer to your question is you did do something wrong when replacing the VCR.
So, open the cassette door, carefully push the metal box into place. When the metal box is placed correctly the cassette
door must follow the metal box so to speak. If neccessary, metal box may need to be pulled backwards a little for the cassette door to open correctly.