Strange retargeting glitch

Hello, I have a weird glitch that has been occurring on my Advanced Locomotion systems v4 based character that has been occurring since I imported a mixamo animation.
When I start the the editor and PIE my character will be tapping his left foot at a regular pace. If I then open the skeleton, delete one of the added sockets or bones, then play, the problem is fixed. I then go back to the skeleton, paste back in the bone/socket and everything is fixed.
Whatever the problem is, it seems to resolve itself after that, until I close and restart the editor. Any ideas would be appreciated. Haven’t tried out what happens in a build yet.