https://community.adobe.com/t5/photoshop/problem-with-brush-strokes-appears-to-be-stamping-not-match...
Photoshop 21.0.3 As described in this thread, ever since the most recent update, bristle tip brushes will produce uneven, broken strokes like this:
I've completely reinstalled photoshop and reset all preferences, so the issue seems to be entirely unrelated to any possible brush or tool settings, and appears to occur with the legacy bristle tip brushes only (however I'm not 100% sure about this, it might just be harder to tell with erodible pencil tips or the airbrush).
I've been very happy with these brushes in PS so far and can only hope for continued legacy feature support in this regard, as I intend to continue using them for a long time to come.
Thanks in advance for the help!