Could it just be rotting infrastructure? I.e there is some logic on most visited domains to allow ease of moderation, that logic is read heavy and is now bucking under skew.
>>snake_+(OP)
A few years ago I remember their URL shortener on android app directing somewhere that my hostfile adblocker would catch (like an analytics domain or something). This made it so first click on certain twitter links would fail, but if I clicked it again it would go successfully. Ultimately I never researched it deeply enough but my guess is they had some sort of handler that would log whether loading their analytics service failed and serve up the direct link on the second attempt.