I think the argument is whether or not current limited cells are the cause of the hyperoxia incidents, or if it's just lack of awareness by the diver, or some other malfunction (stuck solenoid, etc.). Not simply hyperoxia itself.
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Hypoxia for any reason over hyperoxia by reason of current limited cells.
I think you had that one backwards. Limited cells cause the rebreather/diver to inject more O2 into the loop thinking their ppO2 is low.
While not a complete list, hypoxia and hyperoxia are about par with medical events far exceeding both.
Dive fatalities - DAN Annual Diving Report 2012-2015 Edition - NCBI Bookshelf
I've heard about an order of magnitude more incidents about hypoxia for any reason than I have about hyperoxia due to current limited cells. How is this backwards?
This is not CCR-specific data. It doesn't look like the CCR causes are broken out but I may have missed it.
What davehicks posted isn't wrong, it's just incomplete.
If your sensors are that far off in the middle of a dive, then end the dive. Don't put yourself in a critical deco situation if things are square. Back on the surface Recalibrate at 100% o2 and check that they read 21% in air. Then you will know if your sensor is failing or just had an intermittent wet connection.