Hi, I just bought a HAC4 Pro Plus. Everything work flawlessly but the altimeter. To be precise, it jumps up and down (some meters) even if it is still on my desktop, and if I press slightly the back (on the battery's lid) it jumps even for dozens of meters. If I press the front Ciclosport sign even for hundreds (I think it is where the sensors is located, but I don't really know). I've tried to take out the battery, to tighten the battery's lid, but not very much changed. I'd like to know if is there something I should try before sending it back with warranty. Thank you.