This weekend my MZ-S and I were shooting landscapes while on a road trip. It was quite warm out, and humid.
I noticed on one stop that the mirror failed to return quickly to position after I released the shutter. I assumed I had accidentally set a long shutter speed, so though nothing of it. Then it happened a few more times (not necessarily all in a row) and sometimes the mirror wasn't fully swung away -- only partially.
Later in the afternoon, when I pulled the MZ-S out again, I noticed the rubber plug on the base of the camera (that covers the battery grip contacts) had melted, and partly deformed. I rolled the rubber up into itself, and removed the plug. It was a complete loss, but the camera was MOSTLY clean, just a few little black smears on the contacts.
I know very well that rubber "of a certain age" turns to goo - especially if it's warm out. I've had it happen before to a few rubber viewfinders. Clearly the MZ-S is now "of a certain age...."
I've never heard of the sticky mirror syndrome before in the MZ-S. It's part of why I decided to keep my MZ-S when weeding out cameras.
Did Pentax use some of this self-destructing rubber in the mirror return mechanism? Or is there something else going on?