When the edit window opens, the graph is resized to be less wide. The line-title text wraps automatically, and the second line-title is over-written:
I had not seen this error for some time. It came back in the last month or so, perhaps as a result of the recent updating that was noted at the top of the https://fred.stlouisfed.org/ page.
This is definitely a glitch that comes and goes. I think fixing something else brings it back.