Same problem here, Suunto Smart Sensor connected to a Race 2. Worked flawlessly for seven months until last Sunday when suddenly the sensor connection dropped after starting the run. First idea was of course the battery, inserted a new one, problem remained. Chest strap is always washed after training, bought a new one anyway, problem remained.
I measured the resistance of the brand new strap and the older one; new one has approx. 1.38 kOhms (2x700 ohms), older one has 2.85 kOhms (2x1.43 kOhms), but up to now I heard that the straps should be good if they are below 8-10 kOhms.
Warm reset of the watch did not help, re-pairing the sensor did not help as well. I have no idea why that happens; the last firmware update of the Race 2 was beginning of April, and the watch performed without any hiccup afterwards.
I did a factory reset last night, will try again this evening whether that helped. Also bought a Polar H10 as backup solution… so that sensor problem cost me more than 100 EUR up to now (btw, 39 EUR for a replacement strap is much more expensive than Polar, they sell replacement straps for 25 EUR).
Suunto wants to sell the Race 2 as a training device for runners - training without a reliable HR detection is no option, though. I do not want to use OHR as well, it’s usually quite a few beats off if I am not just sitting at a desk.
Any other ideas except for “the suunto smart sensor is not exactly a piece of reliable engineering, actually is quite crap”?