Odd question for you...when you wash your clothes are there bubbles and suds? When I had to have my front load washer repaired I was told bubbles and suds are bad for a front load washer. (Which didn't make sense to me, I only used HE detergent and just the recommended amount. All the other stuff I used was also ok for my machine.) Bubbles can do something to the filter, which will make your washer work improperly. And for some washers (especially the really nice ones like yours) it can cause confusion in washing cycles, cause delays and make proper rinsing of clothes difficult. Which could attribute to the clothes not getting clean and stain sticking around.
Our repair man said that most of the time, you can even use less washing detergent than recommeneded. He said you should see very few bubbles during the cycle and non when the cycle is over. And he also warned me to rinse out any milk spills before washing, because milk can cause bubbles too.
When we had problems with our washer I noticed the same thing you are talking about...things just didn't look clean. The stains I was so diligently working on remained. My hubby cleaned out the filter (requires taking apart our entire machine, I hear some machines have easily accessible filters). That helped the problem a lot. Unfortunately, the damage had been done and our filter pump was broken and had to be replaced.
So, if it were me, based on our experience, I'd first check the filter. Then I would reduce the amount of detergent and see if that helps.