I completed Hel Ra Citadel, on Veteran, in Difficult Mode, on May 24th 2024
We completed the Trial in 29:18, but the Time Trial achievement ('Complete it in under 33 minutes') wasn't awarded. I was the Main Tank, and didn't leave the trial of have any issues in boss completion.
We started at about 8:02 PM, UK time, and finished less than half an hour later. Here is a screenshot of the ESO Logs with the time graphs:
And here's the URL link going to the ESO Logs page the screenshot is from:
https://www.esologs.com/reports/DRZ7gr1ycbjhAfHY#boss=-3&difficulty=0&view=timeline&source=5
On that same evening, my trial group beat Sanctum Ophidia on Difficult Mode, fast enough to get the Time Trial there as well, and that did get awarded.
I'm not sure if this issue is intermittent. However, no-one mentioned over Voice Chat about the Hel Ra Citadel time trial achievement triggering for them (and we had some other people who hadn't gotten it yet). Whereas other people, as well as myself, commented on the Sanctum Ophidia time trial achievement being gotten.
(The fact the SO one did pop-up was what made us double-check our HRC speed)