Import of Bookmark file fails silenty

[lambi21]

Describe the bug
When trying to import a bookmark.html file (in this case generated by the Brave Browser, with roughly 430 entries in it), the importer fetches the metadata for the bookmarks. When browsing the list, it just stops responding after some time. But more importantly, when trying to import said file (after metadata has been collected). Nothing happens anymore. Checking the log of the container shows the following entry:
Validation error: ValidationError: "[1].url" must be a valid uri _original: [ [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], [Object ...], ... 430 more items ], details: [ [Object ...] ],

The html itself seems to be fine, a browser can open it without any issue. There are a handful of bookmarks in there which do not seem to be reachable anymore, but since fetching the metadata still works, I would assume that is not the error here.