When attempting to tag a particular post, always got error 0f1e70f6717d8955ff94d3189c85f0df without the tag going through either (was attempting to add "no_sound" tag). The post ID is 1598334.
This occurred between 11:15 and 11:35 GMT on 15/07/18.
I tried repeating the tagging in the same tab, attempting it on a new tab after re-navigating to the post and refreshing the page.
It seems to work on other posts just fine, though I have had a few other error messages this morning adding posts to and from my favourites, but in those cases a few reattempts and they worked fine.
I'm assuming it's something going slow on the server or the like, but thought you should know in case it's something particular with that post.
Updated