InDesign CS3 - Chapter numbers disappear in TOC

Can someone help me with this:

In InDesign CS3 we translated a document using Trados. The document consists of 14 separate chapters and a book.

Now that I want to update the TOC it doesn’t show some chapter numbers. The updated table of contents looks like this:

Chapter 1: Before Using the Machine
Components of the machine ......1 (instead of 1-1) this goes like this until page 18, (only the page number without the chapter number) then from page 19 it appears correctly ( 1-19, 1-21 up to 1-30).

This happens with all the chapters in the entire TOC and we can’t figure out the reason. The settings for the pages that have the chapter number in the TOC and the pages that don’t have it look the same in Layout – Numbering & Section option.
Can someone help us with this please. Thank you in advance.