Undo regenerates each restored plate's cut-offs, which removes the
cut-off parts first. A plate holding nothing but cut-offs became empty
for a moment, so the new-plate sentinel dropped a trailing plate while
the restore was still enumerating the plates, throwing "Collection was
modified". Regenerate inside a PlateManager batch so the sentinel only
settles once every plate is done.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
ajandClaude Opus 5.5
c798be9b95