Same thing here, but I use two Macs for work, one with High Sierra, I believe the other, an iMac, has Sierra (not accessible at this moment, as the office is under construction, I'm WAH for the period it lasts). Both have the problem. It took me a while to figure what was happening, as the red dot is not visible in DW and it causes links to not work, they get the path to the file prepended to the actual link on browsers. What I do is copy the link to TextEdit, select only the link and copy it back, that removes the extra character, but still, it shouldn't be happening.
... View more