I changed names of two segments which I had created. I used % symbol in the new names. After that these two segments disappeared from the 'Segments' page (https://connect.garmin.com/modern/segments). I can still find them in 'Segments' window on desctop, but I can't open them. After clicking on them, I get the message: 'Error. Sorry, but it appears that an error occurred.' I can't also delete them, because it requiers opening.
I also changed names of few other segments, but I didn't use % symbol there, and they work well.