HRM display screen not functioniong properly, hard to read
 

I decided to use my old Polar Favor again for training after 2 years. The display was blank, dead battery. Got a new CR2032 and replaced it. Now the display works, but I can see the actual reading bolder, and the remaining characters weaker but still confusing - imagine "888". It varies depending upon the angle you look at it. I had replaced the battery once before and it worked OK. Could you help me with this? Thanks.