On April 9, my 955 recorded a new lactate threshold of 165hrm. After a few days it changed to some default value 162 in the app and finally today it also changed in the watch April 9 162hrm
All fine for me. After the update I receiver several LTH updates again.
I just want to add an observation: my traing in the past never included 'really' fast workouts. I did intervals at 5k or 10k pace, but no repetitions or something like that. The watch detected LT HR and pace which in my opinion were quite low/slow.
I recently changed my running program and now also do really fast repetitions. This triggered a new detection which is far more plausible now.