And the sensors that fire twice run like crap and will knock your hand off or they may completely confuse the ignition module causing hard starting or poor acceleration if you do get the engine running. Any sensor that fires twice has a problem and is unfit for our use. I've only seen a few of the RCexl sensors exhibit this problem and they were commonly seen in 2014 - 2015. I assume most are out of the system now or will be discovered and replaced. Current production ones seem to be OK.
None of the bad sensors I've seen would show any kind of a blink on the tester. They could only be detected by observing the double spark (which didn't always occur when cranking the engine) or by using a scope. I have some saved waveforms but never published them here as most people really don't care about the subject.