When all other remedies for curing bad smells coming from front load washers have been tried and have not been found satisfactory I believe the source of the smell may well be corrosion of the aluminium spider with the products of this corrosion harbouring ‘water’ that turns foul as described below, or, should no corrosion have occurred the ‘water’ left in the recesses of the hubs of the spiders will, if left long enough, turn foul. here is an image of the build up of smelly deposits in a spider removed from a Frigidaire built machine.
Aluminium, and its alloys, are corroded when immersed in an aqueous solution with a pH value below about 4.0 (acidic) [nitric acid is a well known exception] or above about 8.0 (alkaline), most laundry aids, detergent including HE detergent, borax, bleach (sodium hypochlorite), sodium carbonate (washing soda), sodium percarbobante (found in Affresh and OxiClean), sodium hydroxide, Affresh and OxiClean can have pH values above 8.0 should the required concentrations be reached. At the normal operating levels found in washing machines these values are not exceeded. However when the machine is shut down any water remaining will contain, inter alia, soil from the laundry, products of the interactions between the soil and the laundry aids used, unused laundry aids, and the chemicals found in the tap water. As the water from this mixture evaporates the concentration of the ‘impurities’ rises until such time as a ‘smelly sludge’ develops and/or a pH level above about 8.0 is reached and corrosion occurs.
Prime areas for these deposits to occur are, in my opinion, the recesses found at, or very near, the hub of some of the aluminium alloys spiders found in front load washing machines. The final spin, no matter how fast, will not, in my opinion, remove all the ‘water’ from theses recesses.
Unfortunately the only way to cure the bad smell and/or corrosion in these cases is to strip the machine down, clean it, perhaps modify the spider, reassemble and alter your laundry practices. Not a popular solution I would guess!