[ineedasername]

The typical level of sensitivity is absolutely in range for a single unit to produce a catastrophic event.

It sounds like you may have a low sensitivity factor. The usual starting point for estimating this, along with using the "1800 rule", puts typical sensitivity around a drop of 50 points in blood sugar for every unit of insulin. This based on a weight around 65-70 kilos and 0.5 units/day/kilo.

Of course it depends on other details too, even time of day. (My wife, who uses a medtronic pump, clocks in at right about this level but is less sensitive in mornings and more so later on. her pump is programmed for these time-dependent sensitivity fluctuations )

This level of sensitivity absolutely has lethal potential with a single-unit swing. If you're in the low end of normal at 75 points and take another unit dropping it to 25, this is plenty low to cause a person to pass out and thereby be unable to take corrective action, with lethal consequences, especially if the pump is still delivering a basal dose inching levels even lower.

You might argue that careful people shouldn't encounter this situation, and you'd be right. But it still can and does happen, meaning a hobbyist setup that gets something even a little bit wrong has that same potential.