VO2Max Wildly Inaccurate Misleading?

Hello,

I recently got an Apple Watch (about two months ago). I love a lot of the health apps. However, I have noticed that the VO2Max is wildly inaccurate from doing the calculation using a VO2Max calculator. I'm 43 and my first VO2Max reading was 32. Not the best, but I do eat well and walk over 2 miles a day. A few days later after a walk, my VO2Max was at a 12, then the following reading a 14. However, if I calculate the VO2Max using a VO2Max calculator it gave me a reading of 31 and then 35. Either I'm on my deathbed or something is wildly inaccurate. Additionally I've noticed similar discrepancies with the HR rate monitor. I'll be sitting on the couch relaxing and it will show my HR above 100, but when I check it via a BP cuff, my hart rate is only in the high 70's/early 80's.

I'm curious if I need to check in to a doctor or reset my watch. Any help appreciated.