Had a new kitchen installed with a lot of drawers instead of cupboards. Drawer runners are Blum, so are supposed to be a high quality softclose runner. However when in use, we have noticed that on some of them, if we open the lower drawer, leave it part way or fully open, and then open the drawer above it, that the bottom of the drawer above it hits the top of the drawer below it. Is this normal? 

I often have multiple drawer open at the same time, such is as if searching for something, or moving stuff from one drawer to another. I also think it is worse on some of the drawers since we have begun putting stuff in them, although they certainly aren't overloaded, and some of the affected drawers hardly have anything in them at all. The thing is that some banks of drawers are not affected at all, even when the drawers are full. The kitchen manufacturer has been back several times to adjust things already, and I believe they are adjustable to a certain degree, but it is annoying that we have to keep getting them back, as I would have thought that would all been checked.