Hey, I know this isn't your bug, but I wanted to follow up to let you know that I reported this to Tobii and they have released a new version of their "game hub" software (v3.1.0) to resolve this issue. Not sure if you care, but you might want to put out some sort of communication about it.
I'm telling you because far as I can tell, they haven't put out any public communication about the fix, and their software does not appear to have any 'check for updates' functionality. You have to go to their website and manually download the new version to get the fix. So, I'm assuming I'm the only person who knows about this since they emailed me to let me know they were closing the ticket as fixed.
Anyway, it probably only affects about 0.001% of your player base, but those people could have a slightly better experience in your game if they know to update the Tobii "game hub" to v3.1.0.
Regarding the fix, it looks like they just hide both arms from the viewport when you reach a certain threshold of how far up you are looking.