Can a 99 GU RD28eti engine intermittently lose timing?

My 99 GU RD28eti engine seems to intermittently lose timing every now and again. When it does it sounds louder and lacks power. I've taken it to a few mechanics but when I do it never seems to play up. Any suggestions would be greatly appreciated.

Cheers

Ordinarily I would say no .....

But there is the known problem with the 2.8's where the Harmonic Balancer Keyway flogs out, and the harmonic balancer can fall off.

I would be starting here, as if it is shifting on the camshaft it will affect the crank angle sensor, and thus the timing

Mic