Need help w/ LTHR Guided Test

I all, I saw some older posts concerning the LTHR Guided Test and bugs, but they were all over a year old, so I wanted to check in to see if there was any new info.

About two months ago, I did a standard 30 minute LTHR test. My LTHR bpm was 172 and my LTHR pace was 8:28. Today, I decided to try the Garmin's guided test. I started the test after a 15 minute warmup. Immediately, I was told to bring my heart rate in the range of 175-200. The max heart rate I've ever achieved is 184. So I pushed for four minutes and got my heart rate to 171. Then the watch beeps and tells me to get my heart rate between 200-233. At that point, knowing I'd die first, I dialed it back so that I could try and figure out what was wrong and try again in a few days. I kept running another half mile at a cool-down pace and stopped the watch. It told me new threshold detected. 170 bpm and 8:24 pace. So, question. Why was my watch trying to kill me, and are these numbers "accurate"?