Why does UltraStudio Mini HD display buffer frames in red?

I have an UltraStudio HD Mini with the Teranex front panel, which displays the number of frames in the buffer during playback. Usually this is displayed in black text, but I have noticed that sometimes the frame count goes red.

Does anyone know what the red signifies? I'm guessing something 'not good' but it would be nice to know exactly what.

Resurrecting a long dead thread, but did you ever get an answer? Starting to troubleshoot a 4K mini with similar issue where we're getting image stutter and buffer is dropping to 2 or 1 fr and not recovering without reboot. I can see the red, I'd love to know how specific vs generic that red indication is.