I’ve been using a 49/77mm Heliopan step-up ring to mount my 77mm Heliopan variable ND filter on the Zony 55mm f/1.8 lens. The female threads in the ring had developed a burr that made threading the filter on a little tricky. Sometimes it seemed like it was on firmly, but I noticed that I could unscrew it with very little motion. Not wanting to throw away a $45 step-up ring, I kept on using it.
Today, as I was preparing for a series of tests, I mounted the ring on the lens, and the filter on the ring. As I was clipping the camera to the tripod head, the filter did a swan dive onto the floor and broke into pieces.
So I ordered another $45 ring, and also a $450 filter.