620 Cal auto mech stopping

[Perks]

Hey,

I've got an old 3133 bubbleback that I've been fixing for a while now (I moved house so it's been put aside for a while) just got it back together for timing and I noticed that when the auto mech is detached from the movement it works fine but as soon as it's attached to the movement it won't wind the sping.

If I wind the watch by hand it will work for a few rotations then it stops working again, anyone got any ideas?

Thanks,

Chris