At this point I would take off the train bridge and re-clean and lube all the train wheels. Also the pallet fork. Examine all gear teeth. The balance end cap in the movement should be cleaned and lubed too.
All these things can be done with the movement installed if it is. I use a drop of alcohol and a fine paint brush for the balance jewel cleaning, then add a drop of oil through the hole. Not optimal but better than dirty or dry.
If all that doesn't fix this behavior, you may have a balance truing or poising issue. Fixing those requires some special tools and skill.