Okay not an error 429 or 500 this time and just some noncommittal Error with no real message in a logged-out UI (that also returns to normal upon refresh) that I once again encountered for the first time.
I upvoted this very post, e-five's comment, and then your reply in rapid succession. The first and last actions went through, but there was a circle indicator beside the "More" option on e-five's comment and the page ultimately loaded https://fedia.io/ecf/3871174?choice=1 and thus the error page. We're both on the same instance and I shouldn't be blocking them or running any script that should mess with upvoting btw
After going back from the error page to submit this comment, hit submit button only to be redirected to https://fedia.io/m/fedia/t/552719/-/comment without the comment having posted. I find the page usually needs to refresh to send a message but this was the first time I ended up on a different page when trying to write something?