Skoda Octavia 55 auto DSG diesel 2 litre

Hello, 

Changed the cam belt (had both cam and timing done after 100k miles). When I start the car first thing every day, it judders violently and when it is stationary, in neutral, there is a knocking noise from below the engine, which seems to stop when i put it in gear. Mechanic says it is fly wheel. Would like to know if changing the cam belt after 100k miles has anything to do with it... It used to start smoothly before and there was no knocking noise. 

Otherwise car drives fine, but now the knocking seems to be getting worse. 

Pulley tensioners were changes as that was what the mechanic thought was causing the noise. 

Any help/ advice, appreciated. 

Thanks.