1.2 weird behaviour

Hello, 

Just on as a guest for tonight in the hope that someone can help me with an issue my sister is having with her 2006 1.2 (3 cyl) Polo,

2 weeks ago it lost power on the motorway so it's been down to me to to try and help identify the cause, I'm handy enough with spanners but alas electrical systems are not my forte.

I scanned it with an Autel which has the particular VW/AUDI reader already loaded, although I've a suspicion someone is going to tell me it's still too generic, and I don't recall the the exact code, something like P03** (sorry)

Anyway, the DTC stored at the time was pertaining to the camshaft sensor, so like a silly sheep I replaced it with a cheap trade Intermotor part, not a Hella original, upon fitment it did not run any better tbh, then I brought out the multimeter and tested the resistance.

No reading from the old one whatsoever, but the new part gave me a reading??

Then I changed the plugs, and it improved, left it a day and it ran perfectly.

I'm aware of the potential for these engines to slip a tooth or two on the timing chain, but it cannot be that if it runs normally most of the time, surely?

Any inspired wisdom gratefully appreciated.

Thank you.