Try again but this time follow this workflow:
Once you have the project as you want it save it as a disk image via the File ➙ Save as Disk Image menu option. This will separate the encoding process from the burn process.
To check the encoding mount the disk image and launch DVD Player and play it. If it plays OK with DVD Player the encoding was good.
Then burn to disk with Disk Utility or Toast at the slowest speed available (2x-4x) to assure the best burn quality. Always use top quality media: Verbatim, Maxell or Taiyo Yuden DVD-R are the most recommended in these forums.
If the disk image will play as you intended then it should burn to disk and play satisfactorly in a DVD player. There is a 99 slide limit in slideshows but exceeding that usually results in a pause for a bit before continuning. How many slides do you have in the slideshow?
There's a 99 chapter/slide limit for video DVDs. Apple gets around that limitation by renumbering slide 100 back to 1. At that point the DVD will pause a bit. Different DVD players will be affected differently. My high end Sony DVD player pauses longer than my inexpensive Sony DVD/VHS player. Go figure.
The workflow I suggested does help minimize the pause but can't eliminate it entirely.