We work in unpressurized aircraft, often at high altitude, wearing oxygen masks.  Hypoxia is a risk, and one of the symptoms of hypoxia is euphoria, the feeling that everything is fantastic. To mitigate this, crew members test O2 levels regularly and report them to each other as a sanity check. The saturation, given as a percentage should be enough to get an A on a test, so 87 and up. If someone gets a B, they have to check their equipment and retest in a few minutes.

Before the pandemic, I stocked the planes with Pulse oximeters, within reach of each crewmember, and then had to test them monthly and change batteries, because apparently that's something pilots can't do at the end of their flight. After a few years, a couple of them were held together with duct tape because the Battery Covers wouldn't stay on. So I ordered some more. And they were terrible. I have a box on my desk labelled "pulse oximeter graveyard" where I toss the ones with dead displays, broken springs, pilot-reported terribly inaccurate readings and the like. 

During the pandemic, everyone around the world wanted a pulse oximeter and manufacturers churned out millions of barely functional ones with no durability.  Or expensive hospital grade ones with bluetooth and recording functions I don't need or want.  So I keep ordering a few of a new kind, hoping they will be better.  I laugh because some of them advertise, "no struggling to change batteries, easy-open battery compartment." Documenting those battery covers that won't stay on to make them into a feature. (That's the difference, my programmer friends tell me, between a bug and a feature. The latter is documented in the user manual).

This baffled me, though: