Hello and thanks for trusting me to help you today. I am a licensed diagnostic and repair technician, I look forward to working with you.
This sounds like the extention arm could be putting too much weight onto the switch causing it to flick down into the wrong position, otherwise it will be a fault with the switch, there is a spring that holds it in the central position, if the spring goes weak, it will cause this problem, but as this is since the extention was fitted it may just be the extention, or possibly a combination of the two so ideally the extention needs to be removed to see if the problem is cured, if so it may need adjusting (depending on the type fitted)
when I picked up the car and driving it without the stalk I ask my passenger to indicate for me on ocassions, he found that when cancelling HE over cancelled it also, though not always
maybe it is a combination of the two then
Yes, if that is the case, I suspect the switch is going weak and the extention is worsening the fault.
if I get the spring checked, is it possible in your opinion the get a stronger spring?
the car is only 3 years old (30,000 miles), so surprised if the spring is weakening already?
There isn't much that can be done as it is a sealed unit, I have seen these go weak on several models before so it might be a common issue. My best advice would be a replacement switch which will have a good strong spring.