Lichess Studies - keeping the board in synch with the people viewing the study

When I use the Study feature and invite people to the study, the board sometimes goes out of synch when we look at variations. Pressing the Sync button doesn't always work; sometimes I have to send a link to the study. How can we look at variations in a study and maintain synchronization?

I'm interested also. And where is the Sync button?

It's the checkmark button just below the a1 square of the chessboard.

@ReleaseTheBats Thank you!