Hi, I actually have the same issue as you. I’ve created a new idle stance that was built off the third person starter package and it is twisting the leg (as you can see the in the picture) when I override the default idle in a duplicated ABP - this doesn’t occur in the animation. I’m looking around for a solution so I’ll let you know what I find.
edit: Mannequin Feet Not Moving During Custom Animations - #2 by L.F.A