PRAGUE, July 22 (Reuters) - Volkswagen"s (VOWG_p.DE) Skoda Auto will cancel several shifts ahead of the car maker"s annual general two-week leave, as lingering shortage of parts blocks production, trade unions said on Thursday. The annual leave is scheduled for the first two weeks of August, but some shifts will be cancelled already as of July 28, the unions said in their weekly magazine Skodovacky Odborar. Skoda had no immediate comment. The company has already cancelled some shifts in June. Car producers across the globe have been struggling due to disrupted delivery channels of parts, mainly chips and semiconductors.