Tamron 150 - 600 Mk1

My lens has started switching itself from autofocus to manual. It happens after around 5 to 10 seconds after I switch the camera on unless I keep pumping the autofocus.
I have seen other threads on this but there is no clear fault or fix on them. The lens was updated to the latest VC firmware by Intro 2020 a fair few years ago.
It does seem like a firmware issue to me rather than a mechanical one as the lens works perfectly apart from this issue.
Any ideas / thoughts?
Also if anyone fairly local to Southampton has a Tamron Tap-in console (Canon) I would be interested in flashing the firmware back to the original to see if that makes a difference before I think about changing the USD motor.
I have seen other threads on this but there is no clear fault or fix on them. The lens was updated to the latest VC firmware by Intro 2020 a fair few years ago.
It does seem like a firmware issue to me rather than a mechanical one as the lens works perfectly apart from this issue.
Any ideas / thoughts?
Also if anyone fairly local to Southampton has a Tamron Tap-in console (Canon) I would be interested in flashing the firmware back to the original to see if that makes a difference before I think about changing the USD motor.

Hi, thanks for your response, I've cleaned the contacts & tried it on another body with no joy.
Suppose it must be a USD or VC problem but I just find it strange that it switches itself to MF when the physical switch is set on AF - Like you would do from the Q menu rather than throw up an error code.
Suppose it must be a USD or VC problem but I just find it strange that it switches itself to MF when the physical switch is set on AF - Like you would do from the Q menu rather than throw up an error code.