Everything about endnotes makes me want to bang my head against the table. I don’t do them much, but people tell me that Peter Kahrel’s scripts are invaluable: https://creativepro.com/files/kahrel/indesign/footnotes.html

You can learn more here (requires membership):

Working With Endnotes in InDesign

and

Peter Kahrel’s Long Document Scripts for InDesign

I wonder if it is this problem:

Words Hyphenating Wrong in InDesign

But also, because you are using a 3rd party hyphenation tool (which one?) it may be that software, not InDesign?

When you say the column letter designations are not consecutive, do you mean the letters that Excel provides along the top edge? If those are not consecutive, then there’s a chance that some are hidden. You may have to right-click on the boundary and choose “Unhide” from the context menu.

Another option is to export as CSV and then open that CSV in Excel… that way, there should be no formatting at all.

Here are a couple other articles to look through:

Troubleshooting Data Merge Errors

Zap Gremlins in Problem Data Merge Files

Thanks, Steve… just FYI: our forum catches posts that have more than 2 or 3 hyperlinks in them and holds for moderation (to keep spam down). But I clicked approve. :-)

Interesting problem… normally, I would recommend using a Nested Style instead of a grep style for a run-in head like this. But the fact that sometimes there are URLs definitely makes it harder.

But for anyone reading this who is curious, here’s the nested style approach:

InDesign How-to Video: How to Automate Run-in Header Styles