[Affected versions]:
Beta 78.0b7

[Affected platforms]:
Platforms: Windows 10

Steps :

1. Launch the Firefox browser and reach https://codepen.io/heypablete/pen/qdIsm
2. Select and Copy the Table header and a few rows.
3. Open Google Document or OneDrive spreadsheet online editors.
4. Paste the selection into the newly opened documents.

Expected Results :
The Header of the table should keep the format.

Actual Results :
The Table header is pasted on the same column with an empty space between the rows

Note: Please note that when copying from Chrome into OndDrive Excel the table header copies in the same column only without the extra spaces, as for when pasting into a Google Document the correct format of the table header is kept.

Mirko, can you, please, take a look at this? The partial vs. full selection results are rather surprising.

I've had a brief look but couldn't see anything obvious. I'll have a closer look at this issue next week.

Although not a duplicate of bug 1639972, it's likely related to it.