I turned off Eversync autosync and turned on Microsoft Edge sync. Things were fine at that point. When I turned Eversync autosync back on, my bookmarks quickly got deleted.  I don't understand what the problem is.

Incidentally, I also have an extension called SuperSorter that sorts my bookmarks and removes exact duplicates.

SuperSorter - Chrome Web Store (google.com)

Are you asking if I installed the Eversync extension in Edge from the Google Chrome Web Store?  I think so. This is the address of the extension when I right-click it:
https://chrome.google.com/webstore/detail/eversync-sync-bookmarks-b/iohcojnlgnfbmjfjfkbhahhmppcggdog

I don't see an Eversync extension in the Microsoft Edge extensions store:
https://microsoftedge.microsoft.com/addons/search/eversync?hl=en-US

Yes, I'm using the auto sync feature in Eversync. I did turn it off immediately after filing this bug report, and since then I haven't lost any bookmarks. 

Meanwhile, I don't understand the rules surrounding the auto sync. 

1. If I use the auto sync, do I have to turn off sync in the browsers?  
2. Does Eversync work with Microsoft Edge?
3. Does Eversync work with Brave?
4. Does it matter which manual sync button I press to start the initial sync (Merge, Upload, Download)?  When I would start with a new computer, I would press the Download button and expect Eversync to automatically do a merge thereafter. Or elsewhere I'd choose "Upload" to put the "master" copy on the server. But then I started to wonder if I initially chose "Upload", would that computer always upload and overwrite the server bookmarks thereafter?

Ideally I'd like Eversync to sync between my browsers on the desktop (Edge, Brave, and Chrome). Then I'd like the individual browsers to do their own sync to my phone. That's how I had it initially. After I started losing bookmarks, I turned off sync in the browsers and only had Eversync running in Microsoft Edge on three different computers. That still seemed to be enough to lose bookmarks.