I use a Microsoft Surface Book. The keyboard on the Surface Book does not exhibit this problem. I have TWO Microsoft Designer Bluetooth Keyboards - one at home and one at work. Both keyboards (one purchased only two months ago) exhibit the same problem when used with the Surface Book. I do not have another type of Bluetooth keyboard to test with.
Again, this problem occurred ONLY after updating to the Windows 10 Fall Creators' update. The problem did NOT occur before.
While it would be optimal to test with a different brand or model of Bluetooth keyboard, given that the problem started occurring at the same time for two people on three different PCs with four of the exact same model of keyboard seems, to me, a smoking gun.
For me, particularly frustrating since I'm exclusively using Microsoft products.