The problem is the double exposure is not resetting after you take the picture because of dried grease. Repairing it requires removing the wind side of the camera and cleaning up the interlocks that control double exposure. I suspect that you don't have as much problem with this on a hot day and more problems on a cold day. The reason it appears to clear up when you focus back and forth a few times is because enough time has elapsed for the interlocks to move (plus the vibration of focusing has also helped).