Candy CBTD H7A1TE-80 – Lint Inside

I had to take apart the tumble dryer as the youngest managed to put a black biro into the dryer leaking ink everywhere over the inside and the clothes. The dryer is 3 years old. When I took the top off I was very supprised to see lots and lots of lint covering every internal surface. My wife and I do empty the lint trap after each load or two.
When I took the plastic front off I looked at the running groove for the drum front where the felt strip is and it was clear to see that the lint has been bypassing through this route. After clearing it all up and testing the drum in this groove for fit it’s clear that the flet does not touch the entire inside of the drum. To me this means there’s an easy air path for the lint to escape near the bottom. The felt does not seem worn.
Q: Is this normal for a dryer?
Q: Is this just a bad dryer?
Q: Should the felt to drum be a good tight fit?

(I cannot seem to upload images – I’ll work out how)