Unwanted format changes on Excel worksheet in SharePoint

Hello - I've been working successfully with an Excel worksheet (.XLSX extension) that is published to SharePoint and has multiple Users viewing/updating data on this worksheet every day.  Today, columns on this worksheet keep reverting back to varying widths (some way too wide and others way too narrow) despite going into the worksheet, re-formatting the column widths and saving the document.  Other worksheets in the same workbook so far do not exhibit this behavior and are maintaining the desired column formatting (i.e., proper widths).

I cannot figure out what is causing this unwanted formatting to happen and it has not happened before.  I'm guessing this is an Excel issue, but might the SharePoint component be a factor as well?

What are the potential causes of this, and what can I do to make the desired formatting remain and not revert back to the unwanted formatting?

Thank you!