Hello,
with rdesktop 1.8.3-2+b1 on Debian 9.8 this problem seems to be solved.
Markus
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Heathrow XT [Radeon HD 7870M]
ii xserver-xorg-core 2:1.19.2-1+deb9u5
ii xserver-xorg-video-radeon 1:7.8.0-1+b1 1.8.3-2+b1
