Don't think so, because the OP says all but two his TOC 3 lines
are okay, and the OP gave a one-word Heading 3 as an example of a
TOC 3 that appeared incorrectly, so that made me think it was an
extra tab stop in the middle rather than a missing tab stop at
the right.

Suzanne S. Barnhill wrote:
It's more likely that the style/entries have lost the right tab at the right
margin.