Originally posted by Pentax Syntax Odd behavior indeed. If you frequently swap out lenses and adapters it could be that the body contacts are dirty or damaged. Try cleaning them. It is a bit tricky since you have the mirror box exposed. Another possibility is battery issues. Have you tried swapping out the battery?
I cut an old white body cap to expose the contacts while still protecting the mirror box. Not perfect but it worked and I felt better (being mostly thumbs) about working and not messing something up worse. Might try that if you have one of the cheap white body caps.