The "Back " functionality will not work if the slide is a question slide and you have unchecked "Allow backward" movement from Quiz preferences.
Make sure you enable them.
This is how it is done:-
1. Follow Edit > Preferences > Quiz> Settings tab. check the option "Allow backward movement" - This should now enable backward movement.
Thanks for your quick reply but my slide is not a quiz slide. It's just a "regular" one. Perhaps you have another idea?
Just thinking about this from a logical standpoint.
You have a playhead that is in motion moving from frame to frame. Along the way it may be stopped at various places awaiting some interaction or it may suddenly be moved to a different position. So repeated (and possibly fast) clicks on the back button might possibly confuse the issue. For example, if the playhead reached a point where it was suddenly supposed to skip to a different slide and you happened to click Back to move it to the skip ahead point. I could see that causing confusion.
All this is pure speculation. But I'm wondering if it's having a play in the scenario you are listing.
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Thanks, Rick, for your advice. This may well be it.