Smelly Washing Machine

Hello everyone

New poster here, and I’m hoping someone can offer some suggestions for a persistant musty/moist/damp smell that appears on a daily basis in our open plan kitchen.

We moved into the house about 6 months ago, and bought a new washing machine that’s now 5 months old. For the past few months we’ve been getting an unpleasant smell on a daily basis that’s worst in the mornings/afternoons and appears to be a bit better in the evening (either that or we just get used to it!).

I’m pretty sure it’s somehow related to the washing machine, which is the only item in the kitchen that smells. We also did a 90C maintenance wash which exacerbated the smell.

So far we’ve:
1) Done 3 maintenance washes at 90 degrees C
2) cleaned the filter, seals, and tray in the washing machine
3) poured sink & drain unblocker down the sink and also the standing pipe (they both connect under the sink, with the dish washer connecting from the opposite direction)
4) Waiting for some Affresh to arrive
5)I’ve disconnected the u-bend and attached piping, cleaned them out, then reattached.
6) checked for rotting food/vermin under the unit carcasses, vacuumed, and mopped the floors.

The smell is really getting on my nerves, particularly as it’s an open plan kitchen/living area. I’m wondering if there’s a drainage problem, given the machine is new and doesn’t appear to have much, if any, mould build up. The drum does smell however.

The washing machine waste pipe connects to a standing pipe with a U-bend, however I’m concerned that the attached piping seems to sag/dip in the 90 degree corner before inclining up to attach to the sink piping. I’ve tried to attach photos to explain.

The second picture shows the white washing machine piping connecting to gray sink piping under the sink. The white pipe leading off to the left goes to the dish washer on the opposite side of the kitchen to the washing machine.

Does anyone have any other ideas???

Thanks in advance!
Cameron