how do I get Hotpoint dryer drum to reverse?

I have a Hotpoint tumble dryer TVM55A.
When the drum is running anti clockwise then changes to clockwise, it changes over straight away.
When the drum is running clockwise then changes over to anti clockwise it starts to tumble very slowly for about 15 seconds+ before changing to go anti clockwise.
Any ideas as to the part required to rectify the problem
While the drum is running slow before reversing I can see the heater element through the back of the drum starting to go red.
I have changed the drum bearing which required changing, but I still have this reversing problem

bww
January 2019