Missing Magnetic Mask mattes

[82West]

Hi,

When cleaning up my library, I chose to 'delete unused magnetic masks' and now the magnetic masks that I wanted to keep (those that were being used/active at the time I deleted the render files) have disappeared. I get the "unable to render: missing magnetic mask mattes" red screen.

The magnetic mask effect still appears in the Inspector panel, and I can see all the keyframe marks where I adjusted the mask on the clip in the Timeline, but I get that 'missing mattes' red screen and I don't see any mask appearing in the Viewer.

Also, the "show all magnetic masks" button is grayed out in the viewer.

The masks are also missing when I open any of the backed-up library files.

Any ideas on how to get them back?