Pumps aren't as fast as they're supposed to be?

I don't know if it's a bug or I'm just missing something, but I've found out something really weird.

My water reserves were slowly dropping, even though by my calculations I had enough (large) pumps, so I watched one of my pumps closely for a full (16 hours) day.

I counted 59 cycles (and some percents). I did this on two separate days, with the same result.

However, that's much slower than the pump is supposed to be:

* According to the description, base speed is one cycle every 0.33 hour, or 3 cycles per hour. * The beavers working the pump have working speed bonuses of +100%, +80% and +80% respectively, which should make 5.6 cycles per hour. * Over the 16 hours work day, this should make 89.6 cycles in total.

So the pump is only working at 66% of its speed (despite saying it is 90% productive) and I can't see any reason why.

* There's some time lost at the beginning of the day, but nowhere near one-third * The pump is prioritized by haulers, so there was no stoppage to clear the output * None of the workers left to get food or water during the day * The water is 1.5 blocks deep, so the pump isn't running dry * The water has 0% contamination, so that's not the problem either

Are there other factors I'm not thinking of that could cause this? Has anyone else noticed something like that?