Fisher & Paykel Smart Drive 508 - problem with warm/hot washes?

My Smart Drive 508 works fine on a cold wash but when I want to do warm it goes to hot and then light starts flashing and it starts beeping. Machine stops for a while, then finally fills and does the entire wash.

I usually wash with cold so don't know how long this has been a problem - only discovered it when I went to do something on Delicate (warm wash), and also when my partner did the washing and set it on warm. It also happens if you set temperature to hot.

It seems to be a known problem (insufficient hot water) as I found reference to it in the service manual which I was able to download; it said it shouldn't cause it to pause. But in this case it does. The hot water at the adjacent laundry tub is just fine.

Insufficient Hot Water (Hot Water LED flashing)
This warning is indicated by the hot water LED flashing. Smartdrive will also be making a rippling set of 5 beeps repeated every 6 seconds. The hot water is not connected or the water temperature is too low. NB. This warning mode does not cause the product to PAUSE