Would love to know which soaps are good and which are bad, and also why hot temperatures help - I would have assumed that high temperatures stress the components more than low temperatures.
English is not my first language so this is going to be hard to get across.
Apparently low temperatures do not fully resolve the modern soap (which is thick and heavily perfumed), leaving behind a lot of residue. An occasional hot wash clears them.
I don't remember the name of the better soap, but basically what he says is that for clothes that are just a bit smelly but not really dirty/stained, modern soap is massive overkill. It also doesn't need all this perfume. Your clothes are fine smelling neutral, they don't have to smell like a day in the Alps.
Would really advise to talk to a local maintenance guy, they can probably explain it much better.
As a layman, my understanding is that soap (or other residue) builds up due to low temperature washing. High temperature washes break down the build up.
I believe most front loaders these days have both a self clean cycle (you're supposed to run it every month or two, it's basically an extremely long hot water rinse+spin that you don't add soap or put clothes in for), and a drain filter that should be accessible near the bottom front (expect black slime if you haven't cleaned the filter recently).
