Herelink RC left stick dead zone

Hello everyone,

Herelink left stick dead (3.7 MB)

In this video, you can see how the left stick of one of my Herelink RC behaves weirdly.
When moving the stick in the down-right position and pushing harder than usual, the measured input jumps into the top-left corner.
Also, when pushing the stick a bit hard from down-right to down-left while staying down, the measured value sometimes does not move.

This RC has been paired with a drone a long time ago, but did not fly a lot. No shocks or “bad use” to report.
I have calibrated the sticks multiple times.
I have flashed Airunit and RC to newer version multiple time and calibrated multiple times after each update.

Could you confirm my hypothesis that this is a hardware problem ?
If not, what solution would you suggest ?
I would love not to RMA this RC, as this always take a long time and my functional Herelink stock is getting shorter every week.