
Sorry, I do not have the answer to why this is happening. I do have a workaround that will give you more stable bullets, though.
This will be a pain, but you may want to relearn how to do bullets using styles.
How to Control Bullets in Ribbon Versions of Word by MVP Shauna Kelly
[http://shaunakelly.com/word/bullets/controlbullets20072010.html
You can assign keyboard shortcuts to you styles and these styles can be saved in a template.