I've just finished assembling a movement and put it on the timegrapher.
Most of the readings are what I expected for the age and condition of the movement, however, in one position it goes nuts, see below.



I expect that with a new mainspring, amplitude could be improved, but finding suitable replacements for this caliber these days is getting harder each time I look.

Any pointers as to what could be causing the positional change?

I've checked the Witschi guide but I'm none the wiser.

 

Sorry, forgot to alert my advisors.

Paging @Archer , @ChrisN, @Deafcon and any other Timegrapher Interpreters.