This has probably been documented, but I didn’t see it in a search of the forums.
Frame breaks on tacet “systems” are displayed in print mode and indeed remain visible on exported PDFs.
I’m attaching a screenshot of PDF exported from Dorico:
Of course, this means this feature is not currently usable.
Does it export if you hide signposts first? Of course it’s a bug, but just wondering if it can be hidden.
Yes indeed, it is still visible with View > Signposts > Hide Signposts checked.
However, it does disappear if View > Signposts > Frame Breaks is unchecked. Odd!
This is indeed a bug, which will be fixed in the next update, whatever and whenever it may come.