I commonly use copy in a terminal window to grab stuff I have to paste. A few times in the last few days, the clipboard has gotten 'stuck' on some old text. I do the copy gesture (with keyboard or Edit menu) in the terminal window. I paste somewhere else, and get something other than what I just copied.
If all else fails, I can always tell the terminal to write it's content to a file and use that. But I'm wondering if there's something I'm doing to get into this pickle and if there's any way out.
This seems to be provoked by having a great deal of history scrollback on the particular tab. Sometimes the next thing that happens is that Terminal crashes.