I have had similar problems with cheep filters. They just do not take as much care in manufacturing as the better firms like Hoya and B&W. I would not recommend WD40 as it seems to have a negative lubricating effect and you don't want it anywhere near the front element of a lens.In the long run, its best left in the garage for the car. Maybe just twiddling them for a bit may be the best option.

Need to give Ricoh a bit of time. They have only owned Pentax for a few hours.

My condolences on the sad loss of your *ist.
I have one and like the camera a lot. Unfortunately even when it was being designed by Pentax, I am sure that they knew that it would be their last new film SLR camera. Which is a shame they did not make it a little bit more robust. My MZ5n seems to be taking the knocks a lot better.

Regards

Graham

Wow. It looks like the Pentax brand is going to get some serious investment from an owner that actually cares about making photographic products. Its not before time. Shame it could not have happened a few years ago.
I have a good a good feeling about the Ricoh purchase.

I have been looking in on this forum for several years, so I thought it was about time I joined.
I have been using Pentax products since I was 12. But nowadays I often feel a bit lonely as we seem to be getting a bit thin on the ground.
I use both film and digital cameras in about equal amounts and own several 'classic' Pentax cameras and lenses, which I try to use as often as possible, processing both B&W and colour film at home.