Xserver crash on using xrandr --scale

I was able to get a Thinkppad Extreme laptop with an internal 4K monitor and a 1920x1080 external monitor (HDMI-0) running i3wm stably using optimus-manager with the startup mode set to nvidia, as suggested in this forum.

I recently tried using ‘xrandr --output HDMI-0 --scale 2x2’ to zoom out the external monitor. However, after about 15 minutes, the Xserver seems to crash with the internal monitor no longer recognized. I can only get back to the previous stable state by rebooting. This seems similar to a problem reported here: https://bbs.archlinux.org/viewtopic.php?id=222272 but I am not not quite clear on the resolution of the problem. There does not seem to be any obvious errors logged at /var/log/Xorg.0.log.

Have any of you run into a similar problem and how did you resolve it? Thanks.

is the intel driver installed or do you use modesetting driver from kernel?

pacman -Qs xf86-video-intel

In optimus-manager.conf:

pacman -Qs xf86-video-intel
[sudo] password for rc: 
local/xf86-video-intel 1:2.99.917+908+g7181c5a4-1 (xorg-drivers)
    X.org Intel i810/i830/i915/945G/G965+ video drivers