Keynote auto advance is not working & long lag transitioning

I'm working on Keynote (version 6.6.1), and I have a series of images to be displayed, but the automatic advance is not working properly. Here are the details:

The presentation starts with a static image and some graphics which will need to be manually advanced to start the series of images. I need the images to stay on screen for 30 minutes (and since Keynote's auto advance timing maxed out at 600 seconds, I have 3 of the same images each at 600 seconds auto advance to make it up to 30 minutes). Then the image will transition to the next one with 5-second-transition. This will go on for 2 hours, then it will end on a static image & graphics (which then will need to be manually advanced to get to the next stage, which is another set of images).

My problem is when I tested it, the presentation is stuck on slide 2, I escaped out of presentation mode and started it again without changing anything, this time it worked, but there is a long lag transitioning between each slides. Before I set the timing to 600 seconds delay I tested it with shorter time interval and it didn't have a problem advancing apart from the long lag between transitions even when I tried it with shorter transition time (the lag was substantially longer than the transition time). I've experienced this lag with a number of other presentations even when there is no delay set on the transitions, and I can't seem to fix this.

Can anyone tell me what causes this inconsistency in the auto advance on and how to avoid this, and does anyone know what causes the lag and how to avoid it?

Thank you.