Copy/cut/paste works normally until a row contains an image

Because this affects new and old workbooks only when a picture is present and survives reinstalling Excel, it looks like a picture-object regression or compatibility issue, not workbook corruption. Use Help > Check for Updates and install the newest production Office for Mac build. In a test copy, select a floating picture and use Picture Format > Place in Cell, then copy the row again. Pictures stored in cells are designed to move with the table and may avoid the failing floating-object path. If conversion is unsuitable, copy the cells without the picture, paste them, and duplicate the picture separately as a workaround. Test the workbook in Excel for the web to confirm whether the failure is Mac-specific. If it remains reproducible, send Help > Feedback with a minimal workbook, macOS version, Excel build, picture format, and short recording. Microsoft’s current known-issues page does not list this exact defect.