windows 10 - shift key no longer working

[mediasoft 0]

just did a windows 10 upgrade on my server-pc, and while the server pc shift key works fine, all of the slaves are no longer recognizing the shift key when pressed. i am not on the latest synergy versions, admittedly.. server is on 1.5.0 and the other pc's beside it are on 1.4.15.. could this be the issue? has anybody else upgraded to windows 10 and not had this issue with the later software releases??