I called and talked to Microsoft Band support yesterday after reporting the latest bug introduced in Wednesday morning's update. So, FYI, the bug report has been submitted and Microsoft is investigated a fix.
If you missed it, two updates came through on Wednesday. The one in the morning came with a firmware update for the band. The one later in the day was just an update to the Microsoft Health app. After the morning update, during a GPS run, the band would pause the running activity and try to sync with the phone. It had never done this before. I took at 1 hour, 35 minute run just on Sunday and this problem never surfaced. It was only after the firmware update that this issue started. You can read through my bug testing and verification here: Possible Activity Bug in Latest Microsoft Band Update.
After writing about it here on Supersite, many others have reported the same thing anomaly. For some, the bug seems to even affect sleep monitoring – which might actually be a different issue, considering that my testing shows a problem only with GPS-enabled activities.
After chatting with the Microsoft Band support representative, he suggested simply turning off Bluetooth on the band during a run so it won't attempt a sync. I'm going to do that today (in the next couple hours) and then report back.
UPDATE: I can confirm that the workaround works. I disabled Bluetooth on the band and was able to complete a 43 minute run.