The party order thing is also way worse than just front line getting pushed back
I've given up on simply bugfixing that piece of logic, and instead wrote a piece of code that verifies every combat whether something went wrong and warns me about it.
By now, I've found two bugs surrounding it. The primary one being that while it stored your initial starting order before combat (so it could reset it later), it would never clear that list. So you'd start every subsequent in the same position as your first combat, which becomes worse if that includes some girls that aren't even in the active party anymore since it persists between dungeons.
I expect some more bugs surrounding it will pop out of this check while I work on other stuff.