Luminance mask

Luminance mask. What happen (short video below)? Can someone help me understand this? Is that Figma bug?

Unfortunately since I’m new here I cannot upload video. However it’s on twitter.

Hey there, sorry to hear you’re having trouble!

It’s hard to tell what’s happening from the screen recording. Please reach out to the support team directly via this form for help: https://help.figma.com/hc/en-us/requests/new

Be sure to use your Figma account email, include a link to the file, and share it with support-share@figma.com, so we can take a closer look.