Odd behavior that took me a bit to figure out exactly what was going on. If using RDP on a client MAC, the modifier keys do nothing (i.e. cannot type capital letters, alt-tab, etc.). Switching back to bluetooth for preferred channel, the modifiers start working again. This appears to only happen with RDP as I checked a number of other apps (even a couple that similarly connect to remote windows systems) and did not have the same issue. Don't know that there's much to be done about this (other than use it with bluetooth rather than network), but this might be useful to other users having the same problem.