Which version? v1.5.2 has resolved all sync issues. If you have a real issue then why don't you raise it on GitHub (https://github.com/xbrowsersync/app/issues), the extension makes it clear how users can easily do this!

I realise it's annoying when you are affected by bugs but this is a free open-source extension that I build and support out of my spare time, yet Firefox users seem to prefer to come on here and leave a negative review rather than seek free help and support the project!!! Over 6000 Chrome users don't appear to follow this behaviour judging from the reviews on the Chrome web store...