I've noticed the following issue when using my Descent G1 while running.
As long as I run in open areas, the watch reports my pace normally. By the time I enter dense urban areas, near buildings, the reported pace drops significantly, to false values. Like, from 5:30 to 7:00. I think it has to do with the GPS receiver.
I use the latest 15.08 firmware (which have other reported issues too...), and I'm not sure if this happened with previous firmware versions. Please fix this, because running is the main activity most users use the watch for.