Sync via firefox account creates multitude of the bookmark toolbar all with different content
I sync the firefox data with my firefox account over 5 devices, 1 Mac, 3 Laptops and one android device.
I think meanwhile I have, beside ever changing content in the top-screen bookmark toolbar another + 50 or so folders in the Bookmarks dropdown list with the name Bookmarks Toolbar or BookmarksBar, all with different content. Some of the bookmarks in one folder are double or triple. Some of these are empty. Some have content... but not complete. looks like these bookmark toolbars are representing the status of the top-screen Toolbar - at different times from the previous years.
I rearrange the top screen bookmark toolbar but next time I open up Firefox they are mixed again.
Clueless
Wšě wotmołwy (1)
I strongly suspect that corruption of your bookmarks might be related to Firefox for Android. My thoughts are that the different separate Bookmarks Toolbar folders used on "Mobile" devices is corrupting data on the Sync server and causing duplication of bookmarks on the Laptop / Desktop versions of Firefox.
When going to fix that "duplication" problem, make sure that you reset your Firefox Account / Sync password before re-connecting to Sync om each device. https://accounts.firefox.com/reset_password That will delete the data which is on the Sync server, giving you a fresh start with Sync; thus dumping the corrupt data there.
Use the Places Maintenance extension to "clean" the places.sqlite file where bookmarks & browsing history are stored. That should fis the corruption on the device it is used on. https://addons.mozilla.org/en-US/firefox/addon/places-maintenance/
And if that corruption has propagated to your other devices run Places Maintenance on those devices, too. If you skip either the Sync password reset or skip one device, the corruption may reoccur.