DV90T6240LH Tumble Dryer only reverses at start of cycle

[Scg]

When purchased we specifically chose this dryer as it had reverse action as a feature, however this only appears to work for a few minutes at the start of the drying cycle. When drying bed sheets this is wholly ineffective and sheets, duvet covers etc just wrap up. Have used dryer balls and varied loads with little effect. 
Is the dryer faulty or is this a feature with this design?

[andy_in_ireland]

Its a Heat Pump dryer yes? - by default / technology of heat pump dryers I thought they did not reverse tumble by design.. this has always put me off (even if I could afford one) the fact that heat pump dryers do not have auto reverse feature. 

Previous technology of Vented tumble dryers and Condenser tumble driers nearly always had auto reverse tumbling to minimise creasing , and with sheets , although sometimes then still used to roll up into a ball sometimes it still helps if the tumble drier has auto reverse/anti crease to help that not happening . 

I always say now with sheets and duvet covers if you have a design of a house with stairs and a bannister at the top then drape sheets and the like over that or over a clothes horse or out on the washing line if you can or indoor washing line that pulls out from the wall rather than putting them into the tumble drier