Have you tried ringing/looking through the files on Lords Sewing website????
I emailed them yesterday and have just got this reply
"Hi Janet
The error message you are seeing on your V3
iic-sensor-unit-up is usually associated with one of the electronic control boards in the machine.
It is not something that the user can repair.
We are still operating mail order and repairs. If you have the original packaging for the machine we can arrange for a courier to collect and return the machine from you. It will be £30 each way plus the cost of the repair."
Firstly i don't have the original package and secondly they cannot say how much the repair will be. As i mentioned i have already spent £100 for someone to supposedly fix this.
I did take the cover of the machine again yesterday and swished the brush around and today i have been running it for 5 hours with no problems. I am hoping it is just a blib that occurs now and again and possibly a bit of dust on the circuit board.
Once lockdown is over i am going to contact the repair man who was supposed to have fixed this and tell him i am not happy.