This car has an intermittent fault light coming on, when scanned code P1346 VVT Range Performance Fault [B1]

The garage has already replaced the VVT solenoid on B1 and performed and engine flush.

I have had a scope on the crank and both cam sensors when the fault occurs and cannot see any thing wrong. I have triggered both VVT solenoids via the scan tool with a scope on them and these trigger OK.

The timing belt is correct and at the right tension.

I have had a visual look at the inside of the ECU.

Apart from there maybe a fault with the mechanical side of the VVT I am at a bit of a loss where to look next.

Regards

Simon