This has hit me hard before as well. I had many Many pieces in several of the groups. It wasn't my file to begin with. And someone had made a bunch of changes in position at the mesh level. Pretty sure I abandoned whatever idea I had. That's always sad, when a failure in software causes you to abandon whatever idea you had.
It should always be noted that when you find a solution to something, that your solution is The solution, or a workaround.
Someone pointing out an issue, then you showing a Different way to do something....well, that's kind of the definition of a workaround. And then Eugen went and pointed out it's shortcoming.
I didn't know why some parts works and some didn't. So thank you for the workaround. But call it what it is, so we can keep developers on their toes.