It didn’t work on my hosted site, and after 7 months of me asking it was never fixed, problem was acknowledged though by @tobiaseigen but we rely heavily on tags for traffic so we had to abandon Discourse which is a shame.
That is indeed a shame. 
Personally, I was very curious as to why one of your tag descriptions had stopped working, but I needed some extra info to be able to dig further.
Though I don’t think I realised you were a hosted customer otherwise I would have recommended you contact @team for some dedicated customer support. 
Just out of curiosity, did you try recreating that tag as a fresh one to see if that could have been a suitable workaround and got it working?
It was a case of some worked and some didn’t, i did contact the team and the issue was ongoing for over 7 months and I was losing traffic so had to just call it a day
Yes thats the point, on my install this wasn’t the case
I suppose it’s a little late now, but I’d have been interested in what those ones had in common. Possibly any category or group restrictions, or whether any had been used in PMs, and so forth. It feels tantalising solvable. 
But I’m sorry I wasn’t more help at the time. And I wish you all the best for your community wherever you’ve chosen to land.
No none of the above, the site wasn’t promoted, was just a small group testing and was basic.