Venu 2 Plus Ascent problems

Hello,

My Garmin Venu 2 Plus shows a wrong Ascent in hiking mode, even though the Elevation profile seems correct !

Example: my Elevation graph will show I went from 1,000 m to 2,000 m and then back to 1,000 m. But my total ascent for this hike could be only 600 m instead of 1,000m. Somehow the ascent gets stuck while the altitude continues to increase when I hike, as it should.

What could be the problem?

Thanks,

Aldric