I have a Pi 3, Mac keyboard and magic trackpad.
I have both of the devices attached to my Pi 3 using the built-in Bluetooth and they both respond, but when I type it misses keys and can get stuck typing one key.
I am testing this with my Pi out of its case and ~ 3 inches from the keyboard.
I don't think it's a range issue as my track pad works with it from ~ 2-3m.
Any ideas?