It's not good news I'm afraid.
The service manual states for F18 " Communication error (3 phase motor): replace power board"
Unplug the appliance.
Wait 15 minutes.
Plug it back in and see if the control board resets.
If not, you're looking at having the main board replaced and programmed to the appliance.
Check it out, see what you find and let me know.
Hope this helps.
Let me know how it goes
Sorry, nowhere near, but yes I repair washers.
If unplugging doesn't sort it out your best bet is to give Hotpoint a call.
They have a range of fixed price repair schemes that include parts and labour.
Get the latest prices and plans from them.