There is a patch for it: https://github.com/serayrosh/FreeRDP/commit/ffa7f0363fa4f0770d0f1ac451d7a5e87d415d7b Although, jessie version seems to have different function name, 'xf_kbd_release_all_keypress(xfc);' instead of 'xf_keyboard_release_all_keypress(xfc);' I've tested the patch on jessie (with corrected naming), and it does not work, Super key is still stuck inside RDP session.
