I have faced some index links problems and I found the reason behind it. I share here as it could be a bug.
I am working in a document with 20 chapters, each chapter is developped autonomously and then linked together in a master doc. (Insert chapter+ include file)
At each chapter index links are defined (insert->link->Index entry).
When the master is created, autiomatic fields for Table of contents and index are created.
When document is updated several times (page formated) the correct page refferences are included.
BUT, if there is an index link pointing to a section subsection. title… texmacs does not calculate the pages number until this link is overpassed. Actually it calculates it, as far as page numbers after the link to the section name are correct. Then the index table shows (?) for links before the section name linked and the correct pages after it.
SOLUTION locate the links in the section content and not in the section name.
Somehow this is coherent, section names already have a link to the table of contents and probably a link to the index is confusing for the program.
Hope this helps someone