When a player character is utilising the new ControllerManager feature and most body parts are set to Massless, when you are facing directions diagonal to the universal X/Y axis, your character will twitch.
Behaviour appears the same with another character (default R15 rig tested)
This issue also occasionally causes flinging when landing, especially on sloped surfaces.
Niche issue, yes? You’re probably wondering how on earth I discovered it, but I was experimenting with the new ControllerManager system in my character so I could customise movement friction. I also wanted all characters regardless of player outfit (due to hugely varying character package dimensions) to weigh exactly the same. To achieve this, upon character spawn I loop through the whole character and set every part to Massless aside from the HumanoidRootPart - which is always the same scale regardless of character package. That’s when the twitching started.
I discovered that setting at least ONE of the feet to Massless = false, the twitching completely stops, so that is my current workaround. My guess is that ControllerManager / Humanoid.EvaluateStateMachine= false now treats the character more like a regular physics object, and massless parts (the feet) being crushed by mass-ful parts (HumanoidRootPart), tend to be forced inside parts due to the weight being infinitely higher.
Workaround: setting at least one foot to have mass