Grooves in the seal / lift sliding door

Good morning,
after I finally managed to clean my lift-and-slide door successfully (an older thread), I have now discovered grooves in the seal. I have attached two photos. One of the door side and one of the counterpart... I can't explain where they come from. Especially since there are more and more; when I first noticed it, there were 9... now we are at 12. Over time, another one keeps appearing.

If the gasket is hollow, a vacuum may form at night due to cooling, which pulls the dents inward from the inside.

Just an idea

Try moving the camera closer (if necessary, press the Detail/Flower button to focus)