Timing belt tensioner failure

[Camp0070]

Back in May my timing belt tensioner stud failed after a cambelt change 6-8 weeks after. After that I investigated the damage into the cylinder head and found the rocker arms were all damaged and so have replaced them all and removed all the old broken parts. I also replaced the cam shafts with secondhand ones sourced from an engine centre. I refitted all the parts, so now the car starts and runs, the idle is ok however the car judders heavily like a heavy misfire, over 2500RPM. and smokes slightly I was told it could be due to the new camshafts. One of the lobes also looks slightly worn. Also Ive been told the camshafts can twist when theres a cambelt failure, therefore they should be replaced to new ones - is this correct? Also wondering if it couldve bent one of the cylinder head valves. Do you have any other ideas?
Thanks

[Crasher]

At what sort of speed did the stud fail and which code code?

[Camp0070]

At what sort of speed did the stud fail and which code code?

I was probably traveling 20 - 25 mph
At moment there are no eml lights on

[Crasher]

Which engine code or the VIN?

[Camp0070]

2.0 tdi pd bkd engine

[Crasher]

I would expect 2 to 4 broken rocker arms at least.

[Camp0070]

In total there were only 2 unbroken rocker arms , however i replaced the whole set.
I had to very carefully take out every broken piece, by also removing the sump & oil strainer.
I painfully & time consumingly managed to collect all the pieces.

[Camp0070]

Ive been told when there is cambelt failure you have to replace the camshafts as they twist, to avoid valve damage

Is this true?

[Crasher]

We have done quite a few and not had a problem. The worst one is the longitudinal installation such as an A4, you have to drop the engine right down to get the rocker tubes out.

[Camp0070]

Yes definitley agree
Whag woulc your opinion be about the camshafts?
Would you say the camshafts need to be replaced after a cambelt failure?
Do these engines usually damage valves when this occurs?