Miele W1113 washer - Intake Fault on rinse (but not main cycle)

[McMuffin1892]

I have a Miele W1113 washing machine that runs great overall but ends up with an Intake fault in a very specific scenario - when I run it with cold water, it will do the main wash cycle just fine, spin fine, do the first rinse just fine, then spin, then it will fill for the second rinse... and just as its finishing the second rinse fill, will stop the cycle with a Intake fault error - the red light goes on, washer beeps like crazy, etc.

But it works perfectly fine if I do a hot water wash, and as I said the main wash and first rinse fills also work fine for cold. Its only the second rinse fill for rinse that fails with the Intake fault. I've tested this enough times now to confirm this.

For context I am running it in a new build home that has only just had the plumbing installed; in a rural area with no city water (so there's a well and pressure tank). Water pressure seems fine with all the other appliances and the pressure switch on the tank is set to maintain pressure at 30-40 psi - washing machine only has a few feet of pipe run from the tank (they're in the same room).