Repeat and breath mark combination causes playback to get strangely out of sync

This issue involves split measures, fermatae, breath marks (with / without pause), and repeats. On opening in MS 4.0 it looks right, but playback goes badly astray. I started pruning these elements out one by one and to my surprise, removal of the repeat is what made it stop. There are 4 examples attached of these progressive stripping trials.

You can open all of them in MS 3.6 and they sound right. And they all sound the same except for the presence of absence of breath mark pauses and repeats. Apparently fermatae and split measures are not part of this, but I didn't try to see if they were enabling or exacerbating the problem.

The fermatae are all set to extend the note by 1 beat and the breath mark pauses are 1 second in the original case and then zero thereafter.

The 4 cases attached are:
(00) the original score
(01) same with breath pause times set to 0
(02) same with breath marks removed altogether
(03) same with no breath marks and no repeat

To see the problem just open them in 4.0 and play them.
1. Oh, set the mixer master volume to +12 db to get about the same volume I get in MS 3.6 (Is that a bug also? Or is there no default dynamic setting? And to get the same volume with 3.6 and 4.0, I need to set 4.0 about 2 notches higher in the dynamic scale than 3.6. E.g. forte on 3.6 is about the same as forte fortissimo on 4.0. For voices, anyway.)
2. Note that the first time through the repeated playback (system1 and half of system 2), it seems normal.
3. On the 2nd pass through the repeat, there are a few hints that something funny is happening.
4. By the time you get to the 3rd system, it has gone completely bizarre.
5. When you get to the 4th test case with the repeat removed, it all goes away and sounds like it should.

I'm a first time bug reporter. I got to this form in 4.0 at Help -> Report a bug. If I've done anything wrong, here, let me know. The "Details" drop-down just below here in the form didn't sound like it was for me, so it left me wondering if I'm reporting in the wrong place. I did a lot of software testing in my working days, so I should be easily trainable in how to be a good bug reporter and test case submitter.