So my 945 took over 4 hours to transfer a 1 hour and 30 minute run yesterday. It wasn't until I got home and A) turned on Wifi upload and B) connected to the Wifi that it finally uploaded the activity.
This is a regular occurrence for my device unfortunately, this "transfer in progress" that takes multiple hours for syncing activities that take less time to run!
I've tried disconnecting, rebooting, etc. Nothing seems to work. The same activities recorded on a much older device (Vivoactive) take mere minutes.
This time I *think* it had something to do with trying to download a course from Garmin Connect Mobile prior to going on the run. After waiting 15min for the course to upload, I finally gave up and just winged it on the route. I suppose it is possible that this "course" gummed up the works but because there is no message other than "transfer in progress" on the device, there is no way to know for sure.
It would be nice if you could see what is in fact being transferred and could cancel it if it something causing an issue. I don't really know what else I can try with this device when this happens.