I had started to make a post about the light lens on the later coaches, but wasn't satisfied with my fix. I did this while changing to LED lights. Now I think that this info may help some of you.
The larger ceiling light cans on the later coaches mount with spring wings, they do pull out hard. The smaller ones have screws mounting them.
I was having trouble getting some of my lens off. After using a "jar opener" like Rick, I lubing them with silicone grease and found that they were still difficult. I also noticed that it was very hard to get the lens turned to where the tabs were in the recess in the lens that would lock them in. I then looked at the lock tabs and thought that I was having trouble getting the lens turned to the lock in point due to the square edge of the tabs on the "lock in side." I then trimmed the edge of the tabs to make a better ramp to twist the lens in. While doing this I found that on quite a few lens, that I though were locked in, that the tabs were ahead of the recess. At that point, even though they felt like they were locked in, I could pull them out.
Stock light mounting tab.
Trimmed light mounting tab.
Tape on lens at the recess for the tab to seat, I later found that with the light on I could see the spot with out the tape.
Top view of lens, the recessed area that allows the lens to push in past the tab shows on the right. The recess where the tab has to be to lock the lens in, is the light area just to the left of center.
This is a side view of the lens that shows the recess better.