If the "fix" was slot size and memory....

How long is your ring tone John (in file)? If it's longer than 40-ish seconds, could you try trimming it down (since it never plays more than 40 anyway) and try the test again?

I'm just thinking that may be pulseaudio is trying to cache the full sound file, and when it can't it loads the default known-small tone instead? Can't hurt to try, especially if you're using a larger file for a ring tone (like an mp3 of a song).