It appears that Ingram's flagging of bullet points is not a common occurrence, and changing the font of the text body might be worth considering as a solution. Typically, bullet points, periods, exclamation marks, and other similar elements are parts of a font family and should not pose an issue or be flagged as images.
However, it is worth noting that Ingram has been known to be overly meticulous at times and may flag things unnecessarily. Since bullet points are merely tiny dots on a page and they appear correctly in the PDF, it is highly likely that you can safely proceed with publishing as is without any issues.
If you have any further concerns or questions, please feel free to let us know.