Could be the cuff.
I have to use an extra large.
My BP used to get up around 180/100 when i was bulking and eating a lot, seems to fluctuate with my bodyweight.
Normally it's around 120/60 ish.
It's weird because my BP will literally jump up over night once i hit 230+ pounds. Once i'm down around 210 it's perfect.
Took mine just now and it's 135/58. After a 6 mile hike in the heat with an elevation change of 2000-feet.