Evidence thus far indicates a problem with the diverter valve -- beeping and fault code occurs ~3 mins into a cycle.

Trying running a load on Perm Press. The problem may not occur if the diverter is the fault, Perm Press cycle runs a different operational sequence that does not make use of the diverter and recirculation function.

Anything daughter did attempting to trigger the hidden music sequence shouldn't cause this problem ... it's coincidental that the problem occurred at that time. The diverter may indeed have gone bad.

Except ... if she happened to hit the right key sequence for changing the machine-size and set it wrong, but that still shouldn't affect the diverter directly.

612 is a 6.5kg/7.0kg machine. To check the machine size
- With power off, press/hold Wash Temp Up, then press Power at the same time.
- Should get 4 short beeps and the panel activates. Release the buttons.
- 6.5kg/7.0kg size is indicated by the Low water level light. 5.5kg is Cold temp light. 7.5kg/8.0kg size is Spin Hold light. If the size is wrong, set it right using the button under the respective light, then press Power to exit.

Playing music is via Demo Mode. This works on U.S. EcoSmart models, can't say for sure about NZ/Aus models (such as your GW612).
- With power off, press/hold Advance, then press Power at the same time. Release the buttons.
- Press/hold Wash Temp Up for a couple seconds to play a tune. Press/hold again for the next tune.
- Disconnect the mains power for about 15 seconds to reset out of Demo Mode.

Hi, can't believe I found this post trusty F&P is playing up after many years of reliable service. Following instructions it would seem I have 4 codes 14, 30, 75 and 1. This was only after using the spin speed buttons up which showed different sequence of lights each time I toggled up. Can you help?

Specific model number please ... or is your machine also a GW612?

There are 16 diagnostic levels, toggled via the spin speed buttons. Only level 3 (Hold and Slow lights on) is a fault code, the others are different info or settings.