In the process of trying to work out what is going on, I have checked and tried the following:
- Power supply - official Raspberry Pi power supply, capable of 2.5A
- Tried a different keyboard (another Apple keyboard)
- Tried moving to different WiFi channels (I am using 1 and 6 in the 2.4GHz band)
- Reinstall Raspbian
- Tried Pi Zero W - same results
Does anyone have any suggestions (apart from turning WiFi off)?