My ipad is refusing to play video, but quick suggestion - if y scale is negative, have you tried setting the gravity in the physics panel negative too?
Yes, I have tried, but negative values of gravity direction do not solve the problem
I converted Japanese into English using translation software.
I am suffering from the same symptoms as you.
I hope it will be fixed in the next version.
You may be able to work around this in a limited way by doing the following
In rig mode
1) Select the entire puppet layer and set the X scale to -100%.
2) Select the Body layer and set the X scale to -100%.
However, it doesn't seem to work if you make the head independent.
I have uploaded a reference video on YouTube.(No Audio))