In tools like Clone Brush Tool i Healing Brush Tool must Alt + Click to set a source before trying to clone. As of version 1.8.4.693, the first click does not set the clone source, or not does it appear in the brush preview. Only the second click set/shows the source. It's a bit annoying and extends the working time. I use One by Wacom CTL-671 (in pen mode), I do not use Windows Ink, with the mouse the problem does not occur.