How can I realign my Levolor vertical blinds?

A few slats in two different sets of Levolor vertical blinds have become twisted, out of alignment with all the rest. They rotate on their attachment pieces, but at an angle with the adjacent slats. There does not appear to be any obvious way to release the attachment piece from the string that connects the pieces and rotates them. If I try to force the slat back into alignment, it seems very likely to snap the attachment piece. What to do? (I had the same problem fixed a few years ago by a professional, but I did not watch him closely enough, and now other slats have become twisted . . .I know there is a trick to getting the slats back into alignment -- can you help?)