isInGroup numbers can get out of sync with the parent controlID

I have a BMML file which has a few elements which have a non-existent isInGroup number. It's a nested group and I assume it got out of sync somehow through ungroups and regroups. Cloning and saving the BMML file doesn't fix it. I have to ungroup and regroup everything before Mockups will renumber everything.

This isn't a problem when using the wireframes in Mockups for Desktop, but when trying to export it using my BMML tool, it gets hung up on the non-existent group number, and I had to code up a fix.