Chemical Smell and Skin Rash/Burn from Heart Rate Monitor


I've been using my Garmin tri heart rate monitor since January of this year and recently it started to give me a silver dollar size rash right in the center of the unit. The first two work outs it happened I didn't think much of it, but then the rash started to get worse and when I smelled the unit it didn't smell of sweat or BO it had a chemically/ozone odor to it. I replaced the battery and washed out (most) of the chemical smell but the rash continued to come back, so I had to discontinue using the sensor. Visually nothing looks off about the sensor, it's just the odor and the rash for now.

Has anyone else had this issue with the unit and is there anything I can do to solve this potentially?