Is this in a particular position? I think (and I'm still pretty new at this) it looks like the balance or hair spring are hitting/rubbing on something. For it to register as beat error, I imagine the timegrapher would have to have seen a fairly sharp noise, so I'd suspect hitting rather than rubbing. However, I think hitting would be more likely to make it run fast than slow, whereas rubbing would be more likely to slow it down. This is where it'd be nice if the timegrapher gave you the actual audio/trace rather than a beep/click. Check end play, and remove the balance cock/bridge to see if there are any tattle tale marks where it's hitting/rubbing.
Hello my name is Jesse Purviance and I stumbled onto this for him because I use forums all the time to learn things. I love mechanical watchers although the world seems to have forgotten about them for the most part I like automatics I have several old automatics most of them don’t work my three newest ones don’t work and those are my daily drivers. And that’s why I’m here I want to either learn how to repair them myself or find a place that is reasonably price to repair them. I have a seiko a couple old rados and My favorite watches which I care the most about repairing are 2 maratacs and one Hamilton. They are the main reason I am here the maratacs have the same problem the second hand has fallen off of them but one of them I had a local shop repair and since then it won’t stay wound. The Hamilton face has rotated on it is my every day driver my favorite watch I am a farmer and I am hard on watches Because I am left-handed and I wear my watch on my left hand. And working on equipment and things I swing a hammer a lot which seems to be hard on mechanical watches. Anyway good to meet y’all hope to learn a lot here.
Saying the following is probably like swearing in church, but I use a simple but steady electrically elevated and lowerable table as my workbench (IKEA I think, yes I'm Swedish). I find it extremely convenient depending on what I'm doing, for example fitting the balance cock (elevated) or when I need a "helicopter" perspective (lowered). It quickly goes up and down with a simple press on a button. I'm so used to it that I don't even think about it.
Then again, I don't use eye loupes either but magnifying glasses and a stereo microscope. I would never be accepted among real watchmakers Anyway, I'm truly impressed!