Hemoglobin Sensor Accuracy?

I’ve been donating power red regularly. I’m O+ so I know it’s always in high demand and I’m glad I’m able to help fill the need. My hemoglobin has been over 13.3 every time so I’ve never had a problem donating. At least not until recently when our local Red Cross started using the sensor. First time I used it was in Feb and I measured too low for power red, but was able to do a regular blood donation. I did a regular donation yesterday and it was lower than usual again. I started taking iron supplements after the first time thinking it was me, but now I’m not so sure. I am beginning to wonder about the accuracy of these sensors.

Thoughts?