Vivaldi losing all tabs quasi-randomly on close - Fix / other options?

This is a weird thing that’s been happening for the past week-ish.

My workflow is that I have a “main” area for most of my non-specific web browsing, and a bunch of Vivaldi “workspace” sections for various clients, more serious projects, etc. Vivaldi is configured to suspend tabs after a period of inactivity, so I can basically leave the “workspace” areas at whatever point I finished working on a given project.

I’ll usually be able to close Vivaldi and re-open it just fine, with all tabs intact. But a few times this last week, it opens with all the tabs in the “main” space gone. Gone, gone. Not “closed and recoverable by clicking the trash can icon.” The setting to start Vivaldi with the “last session” is still checked. The only extensions I have are 1PW, Choosy, and Anybox. I can’t imagine any of those being issues.

What’s weirder is that everything in a “workspace” seems to be fine. Nothing in the “main” tab area survives though.

Sometimes I close Vivaldi manually. Sometimes QuitAll/Quitter closes it. There doesn’t seem to be a pattern regarding how it’s closed.

Has anybody else had this happen? Any suggestions as to a fix?

Barring that, is there a browser extension or something that gives a better backup in case the browser torches the tabs upon close?