Oscillating Tripod Theory...

If I have seen something similar to what you describe, it was the tripod shaking, the problem with mirror lenses is the magnification/weight. I have seen this with mirror lenses and with other lenses with teleconverters.

--
Chris.
A weather sealed ultra wide, is that too much to ask?
http://www.pentaxphotogallery.com/chriside
GMT +9.5
Pentax SLR talk FAQ
http://forums.dpreview.com/forums/read.asp?forum=1036&message=23161072