Permanent seconds hand on analog swatch, hand always blinking, pb onPartialUpdate ?

Hi,
I did not understand everything in this new feature, "onPartialUpdate", but I've read the sample on connect IQ SDK 2.3.3
I've succed to make something nice on simulator, without timeout. It work very fine on simulator
And of course, I have no new swatch model, like F5 ou FR235 to test
All the returns from users, for my watchface says that the second hand is blinking, about every 2 seconds
Someone has perhaps an experience like this and a idea of the causes ?
I've cheked the colors, it seem to be OK, ans once again it's OK on the simulator, my second hand is always present with the good color

Thanks a lot !!