Soap left in Smeg washing machine

Yes!
It was particularly noticeable on towel washes. I ended up doing about 12 rinses once to try to get rid of the soap bubbles.
I then ran a cycle with washing machine cleaner (I used Siemens cleaner as my machine is a Siemens but other makes are available).

It is expensive but it seemed to do the trick, but I also found that using Fairy gel capsules produced more foam than other types, so tend to avoid those for towels now.

My skin seems to be ridiculously sensitive to laundry residues. I've been avoiding any laundry powder containing perfume for years but I was still getting odd skin problems that I couldn't narrow down to anything else. So I now put a small amount of washing powder in the prewash compartment and do a prewash, then a main wash using just water, 60° for some things (towels, bedding, etc), 40° for others. It seems to have made the difference. Clothes also feel softer, even without fabric conditioner which I only use on acrylics (mainly Minibags's stuff).

You should do a very hot wash from time to time to clean your washer. I usually do towels or bedding without any detergent.

Most recommendations of quantities are too large, my dishwasher engineer said to use half that amount in dishwasher and washing machine because the pump can't cope with all the foam

I never use powder, I only use washing machine liquid, and then less than the amount recommend. I have an Indesit machine. I gave very dry skin, and like bags I am quite sensitive to many brands, they make my skin itchy!

My DD and I use a particular liquid for our family's sensitive skin but both our machines got very mouldy gaskets despite regular wiping. The local repairman who replaced my DD's machine's gasket, told us to do one 60 degree wash a week for towels etc. using powder detergent ( non bio is fine). I have started doing this with a small load using the same brand but powder version and pressing the extra rinse button. So far no noticeable effects on the family's excema and my machien's gasket is looking better.