what is this?

[kiberbox //]

line flashes red. What does it mean?

[Tom Borovskis]

Point controllers are placed at fixed distances between each other. As the program calculates character motion, it tries to keep these distances unchanged, but this is not always attainable. In case distances between point controllers are distorted, edges between them change their colors.

Stretched edges are marked red, while squeezed are marked blue.

https://cascadeur.com/help/rig/rig_s..._and_squeezing