Only happens for Cannon projectiles.
Cannons combined with the momentum effect (push, pull, stop) or the EMP effect, will decloak and dejam a **shielded** target.
As long as your shield is up, this should not happen.
The damage display number when using these cannons + effects is a **Red** number, the shield is ignored when using a 100% effect. Yet when you use a 50% effect or something similar, you see a red and blue number at the same time.
Perhaps this is a simple < versus <= issue?