Need help with an AABBB arrangement, please.

[dflat]

...
I can edit the double bar line back and forth and this good-play, bad-play switch happens every time.

They appear identical, but No. 1 works correctly, while No. 2 doesn't.
I do realize that there may be other ways of making this particular arrangement play correctly — this is just the one that happened to occur to me as I was making it.

Yes this is a bit odd, but you have not used a closing repeat at the end of the 1st time ending which is what the player is expecting to see. I cannot remember ever seeing a 1st time ending without a closing repeat, they might exist but I am not sure they are very common because generally you can simply use repeats (unless it has a complicated form or nested repeats etc.)
So we did not check the behavior of the location of the double barline for this instance.

Just to make it clear to anyone else following this thread, here is a way to have the form, by changing where the opening repeat and segno are:
(I think this is what you would have done already Jack?)

BBB more correct - Borodin-Forrest-Wright

[nimbleswitch]

Yes this is a bit odd, but you have not used a closing repeat at the back of the 1st time ending which is what the player is expecting to see. I cannot remember ever seeing a 1st time ending without a closing repeat, they might exist but I am not sure they are very common because generally you can simply use repeats (unless it has a complicated form or nested repeats etc.)
So we did not check the behavior of the location of the double barline for this instance.

Just to make it clear to anyone else following this thread, here is a way to have the form, by changing where the opening repeat and segno are:
(I think this is what you would have done already Jack?)

BBB more correct - Borodin-Forrest-Wright

Hi, dflat-

I wonder if you noticed that your form suffers from the same quirk as mine? You inserted a double bar at the back of the 2nd Ending. But if you go in and remove that double bar and instead insert it from the front of the next measure (i.e., the Coda measure), when you play it back it goes straight to Coda and out — no repeats.

I guess the lesson is to make sure to insert the double bars at the end of a section, not at the beginning of the next section — at least in an Ending. Maybe in other instances as well, I dunno. Anyway, as long as we're careful to insert double bars at the end of the last measure in the section, either of our forms plays well in playback. It just becomes a matter of which form you prefer to see on the chart. I'm no musician or musicologist, so I don't really know, but I think I like the looks of yours better, for some reason.

[dflat]

I wonder if you noticed that your form suffers from the same quirk as mine?

I am not surprised, no I did not check. As I finished that measure, I just inserted the right barline to end it.
We will look into this quirk, thanks.

I'm no musician or musicologist, so I don't really know, but I think I like the looks of yours better, for some reason.

Mine adheres to music convention. Your way could be valid (although not usual - like I said, I have never seen it) but there is no reason I can think of to have it the way you had it when it can be done in this way.

[nimbleswitch]

While we're on the subject of the numbered Endings, the phrase, e.g., "D.S. al 3rd End." won't fit in a single 4-bars-to-a-line (system) measure, but I've found that you don't need that entire phrase. Just "D.S. al 3rd" works just as well on playback and will fit in one normal measure. Caution, though, as others have pointed out, there's no guarantee this will work in future updates or versions.

[DaleMac]

..."D.S. al 3rd End." won't fit in a single 4-bars-to-a-line (system) measure...

If you're placing that on the far right measure, it can run off the page and the Player doesn't care. (But someone else trying to read the chart might care.)

[nimbleswitch]

True. I'm pretty used to just "D.S. al 3rd" now for my charts anyway. I've been using the 3rd Ending lately instead of the Coda, mostly because my charts are full of lyrics and the Coda sign seems to plop down in the middle of lyric text too often.

I'm about halfway through converting my lyrics charts over such they are more like dflat suggested, except using a 3rd Ending instead of a Coda. So I suppose my charts are still not going to be conventional -- but they're just for me anyway.