VBox with page break followed by HBox followed by VBox won't actually display the HBox and shouldn't insert additional blank page

The score VBox-HBox-VBox.mscz was created in 2.3.2 and consists of a VBox with a page break, followed by a HBox, followed by a VBox. It renders correctly in 2.3.2 and looks like:

However, opening that score in 3.0rc looks like:

Two problems: 3.0 doesn't display the HBox at all (not the text nor the dotted blue rectangle). And it inserts an additional page in between the two VBoxes, when instead the HBox and remainder of score should be on the 2nd page, without a need for 3 pages.