When I try to insert a special symbol (eg. copyright) to a Cwicly P block in HTML mode I get the error “This block contains unexpected or invalid content - Attempt Block Recovery” when switching back to visual mode. If I click ‘attempt block recovery’ it just converts the special symbol code to plain text.
Gutenberg doesn’t provide all the necessary attributes to correctly modify some Cwicly blocks when in HTML mode. This is why it returns the error when switching views. Most of the time, block recovery will apply correctly but will escape HTML characters.
I recommend you insert the copyright sign directly in the visual mode or use a code block.