Sign clipboard modifying after pasting 3-5 times

When you place a sign block and then paste text from your clipboard (to speed up things) the text formatting gets corrupted. It works ok up to 4 signs (4 jobs of copy pasting), the 5th one is corrupted. (See attachment 1)

Checked the clipboard, by pasting in a notepad and you cannot paste again

It seems Minecraft is modifying the clipboard as well although it shouldn't.

The text copied from clipboard is standard codification UTF-8 (See attachment 2). It's spanish for "DANGER: DON'T TAKE OUT BLOCKS!"

I have to copy again and keep going...

In a private 2 people Realm BTW