I'll check my manuals tonight. Mine is finicky about the drum sensor sometimes too. Usually reseating the drum or fiddling with the two metal needle-type sensor wires to make sure they are making contact cures it. It should be possible to program the 7-step if need be. I think holding down one of the buttons when turning on enables the programming mode where you can switch between E6 programs. Shoulnd't need to drain/flush before processing, I dont' think.
It's a great unit, couldnt' be happier with mine!