Bus spotter of the year.
We have a lovely tabletop dishwasher, purchased from korenwolf and
megabitch a few years ago. It's done us fantastic service and is definitely my favourite appliance ever. Unfortunately, it's recently started leaving white residue on everything. Can't tell if it's limescale or tablet residue. Running the machine on an empty cycle doesn't shift it. Running the machine on a quick cycle with just rinse aid doesn't shift it. It's had several runs of dishwasher cleaner (limescale remover) that leave it good for the first wash and bad thereafter. We also keep an eye on the salt. Given that a dishwasher isn't a deeply complicated machine in principle, what else is there we could pay attention to that doesn't involve giving the nice repair man far too much money?