Look familiar?
What’s happening is client sees you are overweight and each time you try to move, requests are sent to server “this is my weight, what’s my movement speed?” at 0-delay intervals which causes the de-sync/stuttering.
Click for technical speculative stuff. potential fix.
Combat de-sync now is the same: your status is “rooted” or “in ice shower” or “charging with GA” or “walking after shooting with fire staff” and while you are in this state, client is coded to keep spamming server to give you your updated movement speed without any delay between requests causing the stutter/de-sync.
The fix: have it when a movement speed change is approved by server, have a cooldown server-side to when it replies to client to actually update your movement speed. Client can keep spamming the “what’s my movement speed” request as fast as possible, but server only replies back an affirmative “X. now update your movement speed” at a delay. This keeps it still server authoritative, just with some sort of new CC diminishing return effect.
This bug was likely introduced when movement speed on roads was implemented, as this required checking if you are on a road, consistently + push for server authoritative checks. When this was patched, the overweight bug also changed from not affecting your movement speed at all to this stutter de-sync walk.
If this is the real cause, and the patch above fixes works, this would not only fix the de-sync/stutter bug but free up network bandwidth which might fix lag in Wars as well. This is also a form of CC diminishing returns that people are asking for (e.g movement speed are checks are on a cooldown). Kill 3 friction points with one fix.