A few things to check:
- Is there enough power? try adding a little power manually a wheel or two up and see if it runs. If it does, then you know the escapement geometry is probably close.
- If there's not enough power, then see if any of the wheels are binding. Check end shake. Gently move each wheel in the train along the axis of the pivots. If one of them "pops", then that one is binding up. It's bushed too tightly or one of the bushes isn't straight.
- If the clock hasn't been serviced in a while, maybe one or more of the bushes is worn to the point that the wheel is so far out of place it can't provide power any longer. The clock needs service: cleaned, bushed, oiled. (All three: just one or two won't cut it.)
I'm betting on power, but it's a little hard to tell from just that one video.
Finally, if the clock hasn't been serviced in a while and it turns out it needs service, don't change the verge/escapement geometry to try to fix it. The only solution to the problem is a good clean/bush/oil service.