Strange timeouts/white popup on redirect

[rugk]

Sometimes the requests time out. Sometimes, it is the already redirected request(or is not it?) and sometimes the original URL given by Mastodon. Firefox then only displays a white popup like and later potentially a network error:

Also the log (go to about:debugging and click on "Debugging" where the add-on is listed) does even show connection errors for that request (note the WebFinger request logged above seems to have succeeded):

Text:

22:43:40.315 could not get managed options Error: "Managed storage manifest not found" AddonSettings.js:65:13
22:43:40.322 Synced setting got for "ownMastodon". 
Object { username: "rugk", server: "social.wiuwiu.de" }
AddonSettings.js:211:13
22:43:40.322 Fetch "http://ostatus.org/schema/1.0/subscribe" for "social.wiuwiu.de" via Webfinger. Webfinger.js:49:5
22:43:45.326 Error: Waiting for request for URL "https://social.wiuwiu.de/authorize_interaction?uri=Ferretsyndicate@radical.town" timed out. NetworkTools.js:156:24
22:43:54.266 Use of nsIFile in content process is deprecated.
NetUtil.jsm:259:12
22:44:22.991 Error: Could not establish connection. Receiving end does not exist.
background.js:1:17097

Note: Both NetworkTools.js and NetUtil.jsm are part of Firefox, so Firefox is actually emitting this error, this is not my add-on. background.js is also unrelated and part of a different add-on.

(Happens with current master and released v1.0 for me.)

Questions:

• Can you reproduce this?
• In which circumstances does this happen? Any special Mastodon server or so?
• Have you ever noticed the same issue without this add-on? (If so how often? I have not…)
• In case you have any idea/clue: What may be the underlying issue?

[rugk]

Or sometimes (this time tested with Nightly), it just stays at about:blank: