Length of played notes when tied across voltas is incorrect and playback is inconsistent

It has been a known issue for a while that you need a workaround to make a tie work across a repeat sign with voltas (involving notes that are no-play and invisible in the printed score). There is however another problem, when the note tied to in the 1st volta does not have the same length as in the 2nd volta, even when it's across multiple bars. Also it is played back inconsistently, as shown in the example file attached.
You will see an example that I ran into in in one of my scores in the attached file: when first played from the bar where the final workaround begins, it plays correctly. But playing from the start it doesn't. This is implemented by abusing a DS with repeats to start at the workaround, then a DC with repeats at the last bar.
Needing a workaround is not so nice, but bearable because it's a notation program after all. But the inconsistency makes the use of workarounds erratic. Is there a bug? Can it be fixed? Please help out.