On the Photon, the clock itself has done it (once or twice – one frame of moving the dot around since I’ve been watching), and more frequently on animations between it displaying the clock (if there’s a dark background).
On the Teensy, I can’t see any red flickers on the background. Went through all the animations and focused on the ones where I saw it on the Photon.
No “apabright” setting (true OR false). Its not in the wifi.ini file.