Blood pressure readings - variabilty

Heart rate variability is a normal phenomenon.
Your Omron is not at fault. Be consistent: sit quietly in a chair with good posture feet both on the ground, Arm outstretched at heart level resting on
arm or supported. Cuff in same position an inch above your elbow.
Relax and breathe normally. There can be enough space to fit two fingers
between your arm and the low edge of your cuff before it inflates. It’s
OK to disregard the first reading and take the one you do two minutes later.
Our BP often varies several numbers from the other side.
You can bring it in to your next office visit and compare readings with their
office as well. Time of day causes variation as well. Keep a record for your
doctor. Most units have a memory.

I have to recalibrate my Samsung Galaxy watch's blood pressure app every 28 days. It's a pain, let's not kid each other, but I guess that is the price the company pays to have the app registered and approved in Canada.

When I do this, I must take three recordings in succession and enter accurately the readings for both pressures in the calibration function. Once the last one is entered, the parent phone app informs me that the app is ready for daily use....again.

But the point is that each of the readings, haven't moved, and have rested for three or four minutes prior to commencing the operation, are quite disparate. The first might read 135/86, the second a couple of minutes later will read 130/82, and the third will rise again to 134/82. I'm sure I am representative of the general population in that all three, done inside of six or seven minutes, will be disparate, but I'll bet the ranges vary widely, some going as much as 8-10 points.

As soon as you think of something that obliges you to act, as soon as you begin to eat a meal, or as soon as you rise from a seated position, you will see a spike in BP and it might last for many minutes. Then, after several minutes of inactivity and being in your 'nothing box' (see that title on YouTube), you'll still have three different readings.

Blood pressure readings change throughout the day.

When I get fitted for a 24 hour monitor at Mayo they take 2 consecutive readings at 3 different positions; sitting, standing and lying down. Often the consecutive readings will vary a lot.

Take your home BP machine to your docs next time and have them evaluate.