Hi there, I'm really sorry for the issues yourself and others have had. This is due to bugs in the syncing code, as well as a bug in Firefox's bookmarks API.

I've been working hard to get all of these syncing issues resolved and have now fixed the known issues in dev, the upcoming v1.5.0 release will include these fixes. Firefox v69 resolves the bookmarks API issues which I've tested in Nightly and confirmed.

v1.5.0 with Firefox Nightly should resolve all syncing issues so please bear with me. Thanks for your understanding!!