"Lock Frame" bumps flows

Project file is here. When I try to lock the frame on the first page, it pushes flows to later pages and changes flow headers.

I can manually add breaks and set the “Wait for” property with no problems.

Any idea why “Lock frame” is doing that?

All that Lock Frame does is add a Frame Break and a Frame Break at the end. The Frame Break at the start is set to Wait For Next.

If there is already a Frame Break at the end of the selection, Dorico replaces it, wiping any properties that were already set.
This has been discussed at length, previously, most recently here.

Tl;dr: don’t mix “Lock Frame” with existing breaks.

Got it, thanks Leo!

Dorico does now maintain the ‘Wait for next system/frame break’ properties on existing breaks at the boundaries of Make Into System/Frame and Lock System/Frame operations, but not under all circumstances. We’ll look into this again.