It sounds like there could be a Jason tab creeping in to your TOC to prevent the tab pushing the number over (or the tab may be stripped by the TOC field). I note there is a \d switch for TOC fields which 'defines the separator between sequence and page numbers'. Perhaps that would be a clue to specify the separator.

Can you post a sample document we can experiment on?

I'm thinking perhaps of a different approach. If you bookmark the various ranges in your document, you could then put a series of TOC fields in which draw from those smaller bookmarked ranges. eg
{TOC \o "1-3" \b rng1}
{TOC \o "1-3" \b rng3}
{TOC \o "1-3" \b rng2}

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Andrew Lockton
Chrysalis Design, Melbourne Australia