C-t n wierdness

Right now I have 4 frames on two screens:

Left screen: frame 0 (left), frame 1 (right)
Right screen: frame 3 (left), frame 2 (right)

If I select frame 3, and push "C-t n" several times (for next window),
eventually after one or two cycles Ratpoison will automatically select
frame 2 without me asking.

Sometimes it will do this after it has cycled the window (frame 3),
sometimes it will do it before it cycles the window (so it gets cycled
on frame 2 instead).

I can't see any other patterns here.

None of the frames in question are have been marked as dedicated.

Any ideas why?
-- 
Brian May <brian-q50s5p6zN2eXcgI2zpBr/[email protected]>