I have FCPX 10.3.4 in macOS Sierra, i use version 10.2.4 before i use latest version, problem showed up when i use draw mask, there some weird black box show up around mask point that i created, i never had this issue when i used fcpx 10.2.3, any help or suggestion will be appriciated, thank you (sorry for my bad english)
this is not compound clip, and yes i used desert glare effect when i made this screenshot, but when i remove the effect this problem is still there, every single clip i try this weird blackbox always showed up
Sorry this didn't solve the problem, and thank you for trying.
Before we go drastic, I would like you to put only one clip on the timeline and apply the Draw Mask filter to it. Then, in the Video Inspector, check the Invert checkbox for the Draw Mask filter. Does this work?