Automatic lactate threshold makes non-sense

Hi all

I’m using HRM Pro Plus coupled with a Descent Mk3i since a couple of runs.

hence now it detects automatically lactate thresholds however the value measured makes nonsense : 

- 5:30 min/km

- LTHR : 70 !!

This value erased all my zones automatically which means I am walking and i am in Zone 5…

my maximum HR is 188, measured automatically.

What’s going wrong with LTHR detection ?

Thanks!