Is any macro ran on your workbook?
If this file is in .xlsm format that store macro, I would suggest you save this file as .xlsx file to have a check.
If you do not click a cell or a range cells at the bottom of the data list, click other location such as row 100+, would this issue be reproduced?
It's recommended to open Excel in Safe Mode(Press and hold the CTRL key and double-click the Excel shortcut) first, and then open this worksheet to check this issue.
I also suggest you go to Excel > File > Options > Advanced > Under Editing Options, the "Enable fill handle and cell drag-and -drop" is not enabled.

Any updates, you could post back.
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