Mitra uses access tokens with an expiration time and when a token expires, protected API endpoints start returning 401 Unauthorized. When that happens, Husky stops refreshing timelines but doesn't show any errors, according to reports from the users.

I don't know how other servers handle token expiry, apart from Mastodon which just generates tokens without an expiration date (issue: mastodon/mastodon#26838). If any of them support refresh tokens, or something like that, I could copy their approach.