Buggish: MS Excel (Web Version) Copy/Paste Issue with message "Retrieving data. Wait a few seconds and try to cut or copy again."

Some days, several brain cells just hate Microsoft. Is it MS' fault? Probably just another underpaid and overworked engineer. But still... why something as simple as copy/paste breaks?

I copy cells then I paste and I get:

"Retrieving data. Wait a few seconds and try to cut or copy again."

Copy something else (not in spreadsheet), paste, correct. Copy same cells again, paste, error message. Paste, paste, paste, paste, paste, paste, paste, paste, paste.... all error messages. Wait... paste... error message.

Sheet has 4700+ records, 9 columns of data.

Reduced record count to 4000+ records.

Now suddenly works.

Unrelated

Copy a cell, select into a cell (ie so that cursor appears in the cell), paste. In the Excel app, this will copy the value into the cell (instead of the equation or type).

This will work on the first cell. Select a second cell and suddenly doesn't work. This happens every time.

Somehow selecting into 1 cell won't delete the clipboard but the second one does. Or probably what is happening is when selecting out being inside of a cell deletes the clipboard. Whatever the case, why is moving cells impacting the clipboard at all?