The simple playlist player is working OK but I need to add a slider to be able to go back to the beginning. When I do this the sound judders. The same thing happens if I use any of the inbuilt players. Am I doing something wrong?

Hello Frances,
Can you, please, provide a link to a test page or a page that reveals your issue?

Strangely it seems to be my computer! I have never come across this sort of problem with it before, but I have tested your demo page on my computer and get the same juddering sound on the same players, but not so on my ipad or laptop.