The frozen key hashes the chain keys, whose seed holds the session's
model, so mattes frozen with SAM 2.1 didn't match in a session on
Classic, such as a fresh effectcraft-cli render, and the frame was
segmented again with Classic. Accept the key under any Roto Brush model
too, as Object Matte has done since #1852. frozen_key is unchanged for
projects frozen today, and editing a stroke or a matte setting still
makes the frozen mattes stale.
JonRC
c08e6f6d5f