Can be a real common problem this happened to me with my last washing machine exactly same age as yours, do you leave the door ajar after washing, I never did, I have new washing machine now after each wash I dry the drum leave door open and dry inside the soap dispenser leave that open only an inch too, I had discovered black marks inside the rim of the seal even though I used to clean inside, it just had an awful smell all the time, despite using well known washing products on the hottest temp to clean, I use Persia powder now rather than the liquids, but was told sometimes the powder won’t dissolve properly, it should do as use it on hot wash, but I do wonder if using some of the thicker fabric conditioners don’t help
