[mf16137]

I have a frigidaire FDB510 dishwasher that the timer stops advancing at the 7 o'clock position (during the hi temp rinse cycle.) If the hi temp wash is not selected the timer runs through the whole cycle just fine. when the hi temp wash is selected the timer stops at the same position and if the hi temp is turned off, it will go on and finish. I was told to replace the hi temp wash thermostat to solve this (which made sense to me after looking at the wiring schematic). But after replacing it, I still have the same problem. Could it be the incoming water is not hot enough? I thought the hi temp selector meant the water would be heated by the element, so this shouldn't be an issue would it?
I am really baffled by this