Toyota AD850 Needle Change Error

HI Guys

I have an old Toyota AD850...it came with a needle case error which I rectified but then straight away it came up with a needle change error. I have replaced the needle change sensor but that didn't fix it...any other ideas as what it may be?? I'm at a loss...the local embroidery machine tech won't even look at it :eek:

I have a needle case error on an AD860 the plate was loose on the left side of the main needle bar shaft tightened it up but had already manually moved the head before i found it how do i set the timing of the head to the correct position now