I've just copied a loop element, which had a data wire going into it.
The internal wires (from the old external data wire) are now black, and I cannot delete them, or re-link them to a new external data wire.
They just don't seem to be selectable any more.
Can anybody give me an clues how I can do anything with them?
It looks like you have discovered a bug. You should report it using Help > Give Feedback.
For working around the problem, the only thing I know to do is to cut the blocks with the black wires and then paste them back in. This seems to get rid of the black wires.
I also discovered the cut/ paste works, but sometimes if you disconnect the block from the loop and then put it back in that works too.
