Why don't change bars in FrameMaker appear in my PDF?

Hello,

I have used change bars in FrameMaker so that reviewers can more easily find the changes made to a document.

Sometimes the changes are rendered in the PDF, but sometimes not.

Can someone explain to me:

• what the possible reasons are for this?
• what can I do about it?

A big thanks in advance!

Kind regards,

Fred Gerke