From the files you sent me, I suspect the problem is not random but related to all text in a table. Is that the case?
If so, it is because you have not applied a style to the content in the table. Try setting it to Normal first and let me know how that goes. It may or may not be that easy but it is an issue I am familiar with.
Let us know if that fixes it.
See www.grainge.org for RoboHelp and Authoring information

@petergrainge
Further testing has shown the CSS used contained print media definitions that were causing this. Commenting them out seems to have fixed the problem.
See www.grainge.org for RoboHelp and Authoring information

@petergrainge