How to get xrandr to output three 1680x1050 video signals over this USB-C dock at 60Hz?

I have three identical 1680x1050 monitors and am trying to use them via the “HP G5 USB-C dock” on my Razer Blade 15" 2018 laptop and its Thunderbolt 3 port. With xrandr I can get all displays working simultaneously sometimes, but never in the resolutions I want to. If I build modelines myself, I can run all three with 1680x1050 with 49Hz. Are 60Hz not possible? Maybe it is a pixel clock issue. xrandr | egrep '^[^ ]' | grep -v 'Screen 0:' | sed -e 's/ (.*//' prints this without the dock connected: eDP-1 connected primary 1920x1080+0+0 DP-1 disconnected DP-2 disconnected HDMI-1-1 disconnected DP-1-3 disconnected after hotplugging the dock I see: eDP-1 connected primary 1920x1080+0+0 DP-1 disconnected DP-2 disconnected DP-1-1 connected DP-1-2 connected DP-1-3 disconnected HDMI-1-1 disconnected booting with the dock shows: eDP-1 connected primary 1920x1080+0+0 DP-1 disconnected DP-2 disconnected DP-1-1 connected DP-1-2 connected DP-1-3 connected HDMI-1-1 disconnected DP-1-6 disconnected With the dock hotplugged I can’t configure xrandr --output DP-1-3 --auto. I get xrandr: cannot find preferred mode. Booting with it works, though. Trying to enable the third monitor with 1680x1050@60 produces xrandr: Configure crtc 0 failed. I even used a modeline generated with cvt -r. I think the monitors are too old for CVT-RBv2. [asking for a friend @bain]