Synced tabs duplicating across browsers

### Which version of floccus are you using?

v5.8.3

### How many bookmarks do you have, roughly?

60

### Are you using other means to sync bookmarks in parallel to floccus?

No

### Sync method

Nextcloud Bookmarks

### Which browser are you using? In case you are using the phone App, specify the Android or iOS version and device please.

Brave 1.85.117 (Official Build) (64-bit) Chromium: 143.0.7499.146

### Which version of Nextcloud Bookmarks are you using? (if relevant)

16.0.1

### Which version of Nextcloud? (if relevant)

32.0.3

### What kind of WebDAV server are you using? (if relevant)

_No response_

### Describe the Bug

I'm syncing tabs across 3 brave browsers. I've got pinned tabs, grouped tabs, and regular tabs. I've seen all of them duplicated, though I only saw groups duplicated ones. I see pinned tabs duplicated regularly, but they show up as unpinned. I think closing and opening the browser is triggering this. The pinned tabs are showing in a grey "unloaded" state when I first load the browser - not sure if this is related.

### Expected Behavior

No duplication of tabs or groups.

### To Reproduce

I haven't nailed down exact duplication steps, but it happens almost every time I close and open brave on one of the computers.

### Debug log provided

- [ ] I have provided a debug log file