I noticed something like this in the last week or two -- the << and >> were completely missing.

I also went to start a new thread about it, but was unable to do so because one of the buttons was disabled (I forget which) -- although it does not seem to have affected TWA884 Replies still worked however, and then I forgot about it.

In any case it fixed itself within a day, so I assumed it was just an errant code update that had gotten rolled back or something.

So while everything is (and has been) back to normal for me for a while, just adding a +1 to OP's datapoint...

EDIT: on reading between the screenshots more closely, if clearing cached worked, it seems likely that that just happened for me coincidentally and that's what solved it.