Table of Contents Order Error

Using threaded text frames eliminates this issue:

https://helpx.adobe.com/indesign/using/threading-text.html

Sometimes you can juggle the position of standalone frames to fix the order issue in a TOC, and sometimes you can't. Threaded frames always takes care of it.

~Barb

These errors are typically caused by multiple text frames on a page, threaded out of order from their visual arrangement. If your content isn't in linearly-linked frames, you'll need to fix that.

And if your content is 'linear' in all ways, there may be a definition problem with the TOC schema. Do you have more than one paragraph style assigned to each TOC level?

It also helps — moreso in the last release or two, it seems — to have a fully defined TOC schema (ID calls it a 'style') under a unique name, saved after each change, and not use the [default] TOC for any listing.