Imbed URL in Message

I like the ability to us the the chain icon in Send a Message to shorten a long URL to a word or phrase, and I use it regularly my newsletter, but over half of the time, it opens with only one line for the URL instead of 2. I have to repeat the process several times to get the 2 lines necessary to create the smaller link. Is there something I am not doing correctly the first time?

I normally write the text of the short link and select it before clicking the link icon, so it pre-fills the text. I don't recall ever having issues with only the URL line appearing.