This is happening because the JavaScript for highlighting was changed, to do the highlighting based on the full move string rather than on arrays of [origin, destination] pairs. The new code is too careless in deciding whether a square coordinate is mentioned in a move string: it uses the JavaScript endsWith method. And when you write 16e as destination in a move, this also ends in 6e. So when it loops through all board spaces to see if these occur in a move that starts with the selected piece, it finds these spurious matches.
This can only happen with chess-style coordinates if the file name would be multiple letters. So it did slip through the testing.
This is happening because the JavaScript for highlighting was changed, to do the highlighting based on the full move string rather than on arrays of [origin, destination] pairs. The new code is too careless in deciding whether a square coordinate is mentioned in a move string: it uses the JavaScript endsWith method. And when you write 16e as destination in a move, this also ends in 6e. So when it loops through all board spaces to see if these occur in a move that starts with the selected piece, it finds these spurious matches.
This can only happen with chess-style coordinates if the file name would be multiple letters. So it did slip through the testing.
Just wait until Fergus fixes it.