Compass deviation on 2 OSTC

[Motardplongeur]

Hi,

I have 2 OSTC (2 & Sport, see ref. w/ my signature) and I have the same issue w/ the compass on both (w/ latest versions, V3.37 & V10.97.

I made the standard calibration on both one month ago (no smartphone around, nor big metal "device") and was OK w/ indications (5 / 6 ° of gap between both and same w/ "real" north, but OK).

Some days ago, on a boat, I made an heading w/ my OSTC 2 (on my arm, stored before close to my smartphone, the Sport is "always" hooked on my wing as spare, rarely close to a smartphone) and start my dive ; under water, I noticed strange values on my "2" compass. After diving I checked and the gap btw both OSTC was approx 20°, and my Sport was closer to real values.

Today, I decide to calibrate once again both OSTC, w/ same results as the previous one (5/6° of gap) ... but once I put one of my OSTC close (a few cm) to my iPhone, it showed strange values (OK, I can understand, there is a coil inside for wireless charging, iPhone 15, and a lot of "waves"). BUT, once the OSTC far from my iPhone, there is now a big gap (20°), remaining until a new calibration.

So, it looks like both OSTC are skewed "definitely" once they have been put close to a smartphone ; any idea about ?