[Mark IV]

Please feel free to purchase a switch, if needed, wherever you please.

The reality is the unit used by Hi Tech (the factory) is known to wear and have the latching mechanism fail as well as cancelling issues. That you got 13 years out of it is to your benefit. Obviously, a 13-year-old car with 500 miles will have less degradation than a 13 YO car with 25,000 miles.

I suspect when you remove and inspect the switch (and to properly inspect it you must pull the wheel off at the minimum) you will find the pivot points worn with the flat pieces loose on the pivot shafts.

I had the same issue on my 289 MK II which is what lead me to look at several different manufacturers of the switch.