First try the "Disable SetNext support" and see if the behavior changes, then if that doesn't work, also try the "Disable Transport Events option"
Bob,
Thanks for the suggestions. I had exhausted combinations of these options on the releases that didn't formally support the Push Slideshow, so it didn't occur to me to go back and try them.
So I tried "Disable SetNext Support", no apparent effect. I tried "Ignore Transport Events" and bang, the slideshow auto-increments! I unselected the first option "Disable SetNext Support", and the slideshow still works. So it looks like Ignore Transport Events coupled with your new feature was the ticket.
Then, I saw this in the 18.189 Release Notes:
Fixed: DLNA slideshow push. The transition from first to second image in a playlist of images was not happening on the timer properly. This change may also make it more likely to work on devices that were having trouble with the slideshow mode.
Since my setup seemed to exhibit this behavior, I installed 18.189, and disabled "Ignore Transport Events". Now the slideshow didn't work. It froze on the first image at 'transitioning' and was done. (In the prior 18.188 build, I got to the second image (although to me it seemed like the first image transition was short).
So, with 18.189, I tried the options again, and found "Ignore Transport Events" makes it work. Yeah!
And so having made it that far, my next question. How (what settings, if any) can control the scaling of the picture images in Push Slideshow as they are sent to the renderer? From my testing, it doesn't seem like I can get any change or scale effect to take. I'd like to be able to control the fill of my 1080p TV renderer (as it is plasma), and be able to stretch or even altenratively offset smaller images left or right (wishful thinking) so that I'm generally exercising the entire display area.