I have built a Process page in Acumatica working off of a fairly complicated BQL statement with a ProcessFilter of 3 elements. The process works fine, but if you refresh the grid or hit any of the grid controls when one or more of the records in the grid is selected (via selected checkbox I've added to the DAC), you get a "BQL verification failed!" Error citing a PX.DATA.Select2.. string. Why would the line being selected interfere with refreshing from the view?
It turns out that early on I had created a Constant (Zero) that was an Int32 while the field I was trying to compare it to in my BQL for the View was an int. That will trigger the validation error, even though the BQL executes on loading.