[NAME]  When you had triple QHD running, I would bet that at least one of them was not running at its full 60 Hz refresh rate, because the combination of outputs you are using on the WD19TB does not make optimal use of the video bandwidth coming from a system like the XPS 15 9500.The XPS 15 9500 uses DisplayPort 1.2/HBR2 over USB-C/Thunderbolt, not 1.4/HBR3.  (This applies even to your HDMI display, because a chip in the dock would convert the DisplayPort signal from the system to HDMI.)  When the WD19TB is paired with a DisplayPort HBR2 system, half of the video bandwidth from the system is allocated to the "downstream TB3" port at the edge of the dock, near where the system cable attaches.  Don't confuse that with the USB-C port near the HDMI output.  The other half of the system video bandwidth is shared across all remaining ports.  So with your cabling setup and that system, you are trying to run all of your displays from only half of the total available bandwidth, and that is enough for a single 4K 60 Hz display or dual QHD displays, but not enough for triple QHD 60 Hz.In fact if you look at this page of the WD19TB User Guide, in Table 2 for Thunderbolt systems, you will see that for an HBR2 system to run triple displays at QHD, you need to have one of the displays on that downstream TB3 port.  The output combination you're using only allows dual QHD + FHD from an HBR2 system.The simple solution is to move any one of those displays over to the downstream TB3 port, using a USB-C to DisplayPort adapter/cable if needed.
Hi All, I got a XPS 15 9500 and setup with 3 x QHD screens (Viewsonic VX3276-QHD and an AOC Q3279WG5B).  All screens connected via the WD19TB with 2 via DP and one via HDMI. This setup worked fine until couple weeks ago when one screen decided to go FHD instead. (I think it's one of the screen connected via DP). I've swapped cables, etc., and the problem persist. If I disconnect one of the QHD screens then the one doing FHD will do QHD fine.  To illustrate the connection -  DP 1-> Viewsonic - QHDDP 2-> AOC - FHDHDMI -> Viewsonic - QHD I had some driver issues with the laptop as I was fiddling around with drivers directly from Intel so decided to reinstall the laptop.  Now instead of doing FHD, one of the screen is doing 2048x1152 instead.  DP 1-> Viewsonic - QHDDP 2-> AOC - QHDHDMI -> Viewsonic - 2048x1152  The two that are working fine shows 2560x1440 as their Active Signal Resolution, with refresh rate of 59.951Hz.  The other one that's acting up is doing 2048x1152 with 59.940Hz as the refresh rate.  I believe this started before I updated the firmware on the laptop so doubt it's a firmware issue. I'm pretty sure I've had the docking station's firmware updated previously and the screens worked.  This is driving me crazy! Any help would be greatly appreciated - thanks in advance!    
XPS 9500 / WD19TB / 3 x QHD Screens - worked fine but now one failing to do QHD