Yeah that’s I recommended only having the lightsaber fully shut down (masked out) in that brief shot of Kylo attacking her.
As for the malfunction effect, sparks around the handle could definitely help. Feel free to go crazy with whatever effects the actual blade does, though. I would personally do a half ignite with an ever crazier crackle effect.
It would only have to malfunction in that one portion as an indicator that the entire thing is about to collapse.