The reactor isn't overheating, i'm running it with 20% NaOH Solution (1 pound of NaOH per gallon of distilled). Thermal runaway isn't a problem at all after i conditioned my plates correctly, i just can't get more out of this thing without going over the 20% solution and i haven't read anything good about going over 20%.
The only thing I can think of is that with the extra neutral plate and 1/32" smaller gasket i've made the unit more efficient and reached the limit of what i can get out of it.