Ok now this may be a stupid question, but you know I have to ask anyway.
Have you got slots across the bottom and up both sides.? [ yes I know the answer is yes ]
The slop does sound a little much but to test if there is an issue then
you can Very Very Carefully measure between the plates when its running.
You should see little difference between adjacent plates anywhere in the unit.
It will get lower resistance when it gets hot - so the more current.
But that will be much different when you up the KOH percentage to 25%
and you will probably have to run a fair bit less than 2 v per cell once its Hot.
Glenn.