Update (19-DEC-2016): This issue has been fixed in iOS 10.2. If you still have trouble connecting more than two iOS devices to a single Bad Elf GPS unit after updating to 10.2, please contact our support team.
Summary: If you need to connect more than two iOS devices simultaneously to your Bad Elf GPS receiver, avoid upgrading to iOS 10 if you have not already done so.
After several customer reports we've verified that there is an issue preventing more than two devices running iOS 10 from connecting simultaneously to a single Bad Elf GPS receiver. This affects all of our Bluetooth GPS receivers, as well as those from other manufacturers.
Some additional notes:
We've submitted a bug report to Apple and are working with them to isolate the issue. We will update this blog post as we get more information.