Bug affecting system-end barlines, Dorico 4

In the attached (cut-down) file, system-end barlines are set in Notation options to ‘follow barline joins’, likewise barlines at the end of a flow.
When the file is opened in Dorico 4.2, the system-end barlines do not follow this setting: all the vocal staves are barred separately although Voices I–III should be barred together as they are within the staff. The final barline, however, appears correctly as set.
When the file is opened in Dorico 3.5.2, all barlines appear correctly, so the bug seems to have been introduced in Dorico 4 (not necessarily 4.0: I haven’t touched the file between D3.5.2 and D4.2.)
System-end barlines.dorico (654.5 KB)

The project you sent me via email concerning this problem a week or two ago is still in my inbox awaiting my attention. I’m sorry that I haven’t yet acknowledged your email. I have taken an initial look at the problem and can reproduce it, and hopefully this coming week I will have time to take a closer look and figure out what’s going on.