HP Elite USB-C docking not displaying 1440p on external monitor

[loltroll]

System:

• Notebook: HP EliteBook 840 G7 with win10 x64 enterprise
• Docking: HP Elite USB-C docking (TPA-B01)
• External monitor: ROG PG279Q, connected with HDMI cable

Problem:

I do not receive full 1440p solution on my external monitor, only 1920x1080 at 50hz. (edit: I'm also able to set it to 60hz, but that does not solve the main issue)

I'm able to choose higher resolutions like, 1920x1440, 2048x1152 & 2560x1440, but that results in my external monitor going black with the message 'Out of range' on the monitor.

According to the documentation from HP this docking station should support up to 2560x1600 on both HDMI and DP at the same time. 

What I've tried:

• I've updated to the latest Intel Graphics driver. (30.0.101.1994)
• I've updated to the latest HP Elite USB-C docking driver. (1.161 Rev.A, from Mar 8, 2018)
• I've verified that the HDMI cable works, if I plug it directly in my laptop I get the full resolution but via. the docking station I do not get full resolution.
• I've verified that I get the full resolution if I use a display port cable, but my external monitor only have one display port and one HDMI port, and I already use the display port for my desktop PC.
• I've enabled high resolution mode when connected to a USB-C in the BIOS. 
• I've tried unplugging and plugging everything in again.
• I've tried using a HDMI to Display port adapter in the end that goes into the USB-C docking, it only resulted in some of the resolution options to be removed, but I still had 2048x1152 and when choosing this option the external monitor went black again.
• Tried setting my external monitor as main and only having the external monitor active.
• Tried experimenting with 50hz and 60hz. 

Additional information:

I've installed Intel Graphics Commandcenter, and when selecting my external monitor here I get a warning that says something like "Some functionality is not supported on cards that is not from Intel". 
It seems like the intel graphics capabilities are not passed through the docking on the HDMI port for some reason.