I am a recreational road cyclist but I like to monitor my stats for training however I am having a whole lot of trouble with my Giant Neos Pro ANT system. I have had it for 1 year and recently since I changed the batteries in all components the heart rate reading is erratic. Works for about 30mins then spikes to around 240 for a while then works fine then spikes again. I have adding more moisture to strap, moving it to one side giving it a good wash etc. The speed, distance and cadence are all fine. Have I missed something in the settings? or is it a dud system?