URL input disappears and specific feed not added

[slundell]

When trying to add this feed: https://raw.githubusercontent.com/pallih/rss/main/rss/palmemordsarkivet.rss the url input box disappears, a toaster notifications says "Please fix errors before saving". The feed is not added.

I added an example feed from somewhere else, and that works.

I tried to manually add the feed in data.json by replacing the url from the previously entered example feed. Did not collect any items. No errors in the console.

I suspect that the feed I am trying to add is using some odd encoding as it is written in Icelandic, and is generated by scraping a Swedish google doc.