When i patched this bug in my game it wasn’t being replicated through to others in team create, so my theory is that the workspace.Retargeting property just doesn’t save for some reason. Try adding this to your game and see if it works now:
workspace.Retargeting = Enum.AnimatorRetargetingMode.Disabled
Workspace.Retargeting does not fix the issue. It’s AnimationWeightedBlendFix.
You can try to fix it by adding a boolean attribute named “RbxLegacyAnimationBlending” into workspace and set it to true, but I don’t consider this a long-term solution and it does not appear to work in my use case. I’m eventually going to use CFrame for all of my animations in my game and forget about Animator and its problematic implementations.
I had both workspace.retargeting disabled and RbxLegacyAnimationBlending on, all working good 
Actually, this does seem to fix some issues, but the main cause still remains. When retargeting enters its opt-out phase, then we will have issues again.
Hey everyone - sounds like the original issue is resolved, going to close out the topic. If people are experiencing other issues, would you mind filing again? Thanks!