You'll have to do way better than that as far as your description. I for
one have no idea what you're talking about.
I have a document created in InDesign 5 (v7.0). On each of the master pages, there is a button that when clicked will return the user to the Table of Contents page. The TOC is page 2 of the document and it gets updated when I click Layout - Update Table of Contents. It updates based on the paragraph styles used throughout the document. However I've noticed recently that when I refresh the TOC, the buttons stop routing to the TOC and instead just magnify whatever page the user is on. I'm not sure why this is happening though because the TOC page is still page 2 of the document and never moves. Also all of the pages in the document have master pages applied (and the master pages have the buttons routing to the TOC), so it's weird to me that when the TOC gets updated, the buttons essentially forget their designated action (return to the TOC) and just keep the user on the same page but zoom in. Thoughts on how to resolve this?
Try exporting the Indesign document to IDML, open IDML file and export new file. See if this restores the buttons.
For the target of your buttons choose something else but the text contents of the TOC as bookmark (e.g. a invisible rectangle on page 2 or the text frame of the TOC).