Can no longer pancake edit with multicams

For quite some time,  I've been able to pancake edit from multicam sequences using "Open in Source Monitor" then using the source monitor wrench menu to "Open Sequence in Timeline." This would give me a source monitor sequence I could pancake edit from, while selecting camera angles and audio tracks as needed. Super useful workflow. Well, within the space of a single project, I've somehow lost the ability to wrench-menu "Open Sequence in Timeline." I have no idea if I hit some random command that greyed out this option in the wrench menu, or why it might have gone away. But I am 100% baffled by the fact that it has. Anyone have any idea what is going on here?