Comment: I have a large sliding door that is very hard to slide open (need to put a lot of effort into pulling it across). I am unsure of whether it is due to the track (which does look like it some dirt in it but I have attempted to clean and could also be squashed/damaged or misaligned), rollers, or maybe even some settling of our house (which is about 10 years old) and thus shifting of the frame. Hope door can be fixed rather than needing to be replaced.