Gapping pattern

[jdm]

My question is an idle one because I have no intention whatsoever to spend time on this 7S26A.
In 6U position, patter gaps, and then restarts. As if there is an instantaneous slow down in beating. Other positions are kind of acceptable. I know the amplitude is poor but normally does not directly cause this pattern on same movements.

 

 

[rogart63]

Worn bushings for the mainspring barrel? Usually that is the problem when the amp is low? Other then that is the hairspring? But you get good result in other positions so i don't think that is the problem? 

Pallet fork? But again the amp would be higher then?