Karcher WD 2 Plus - Take Two - Same Problem With Replacement Unit?

Karcher offered no support apart from 'send it back'. Which I did and purchased from a different retailer. Overall, same issue seems to happen. This does not happen with a paper or Numatic bag on a different Works Expert unit. I tired using a Works Expert paper bag on this Karcher and the same issue didn't happen. Bags suction power sacrificed for filtration perhaps? Or a crafty way to resell replacement filters...?!