Pasting into lyrics clears clipboard buffer.
If you copy a character into the Windows clipboard and then paste it into MuseScore lyrics, the character gets deleted from the clipboard buffer when you paste. You have to find, select and copy the character back into the buffer before it's available to paste the next time you want to use it. This gets tedious.
Edited to add: MuseScore 184.108.40.20635, Windows 10 Home Edition version 1903.