Latitude 7520, WD19S, P2721Q 4K@30Hz only

@Duschnouk  That should work.  And I don't think you need DP 1.3+ displays to benefit from the extra total bandwidth of an HBR3 link between the system and dock.  If you've already updated drivers, your system BIOS, and the dock's firmware, my only remaining suggestion would be to try a different dock output just in case that makes a difference.  It shouldn't, but you shouldn't be having this issue at all, so sometimes changing variables that shouldn't make a difference actually does.  If even that doesn't work, then this may be a firmware glitch that hasn't yet been resolved.  Just yesterday I was working with someone who had an XPS 13 9310 and couldn't run dual 4K 60 Hz through their WD19TBS, even though that setup should work.  And the previous generation XPS 13 9300 had the same issue at least when it first launched.  Unfortunately not everything that should work in the tech world always does, at least until updates arrive.

Thanks @jphughan for your feedback.

I've tried all outputs, all cables configurations, made all the firmware and software update and still 30Hz.

I'm in contact with Dell staff and I'll keep you posted on this issue.

It looks like the dock was exchanged, same issue. Has anything else been exchanged?

Just a quick note to says that Dell's tech are responsive and that this issue is currently ongoing through private chat.

Right now it seems to be a firmware glitch.

I have been able to reproduce the following (Latitude 7520 + WD19S dock + P2721Q 4K monitor):

• Turn on PC and log on to start Windows
• Unplug all video cables from the WD19S dock and connect the PC to the WD19S dock
• Then connect the P2721Q to the DP port of the WD19S dock, wait for the picture to appear on the P2721Q (DP to DP cable)
• Then connect the P2721Q to the USB-C port of the WD19S dock (yes, connecting the two inputs of the P2721Q to the WD19S dock at the SAME time). Wait for the picture to appear on the P2721Q (USB-C to USB-C cable
• Then unplug the DP cable from the WD19S dock and just keep the USB-C port connected => then on my PC I get 4K 60Hz + USB connectivity

There are some other posts here with users facing the same issue (such as here).

I'm currently waiting for an update from Dell's support which told me that their internal team is currently trying to replicate the issue and find a fix.

@Duschnouk  and @DELL-Chris M Just as additional data points, this exact issue has been reported by two other users who are using the Precision 3560 with a WD19S.  Those threads are here and here.  It does look like there's something going on here with at least certain HBR3 systems and the WD19S.

Thanks @jphughan for your post and the link.

Just a quick note to let you know that I had the opportunity to double check if it was the dock or not the root cause and I think it definitively is because:

• I tried with a Latitude 7320 with the exact same setup (WD19S and P2721Q screen) and the behaviour was exactly the same and reproductible (4K 30Hz unless using the double cable connection trick)
• I tired with the Latitude 7520, WD19S dock but with a BenQ EL2870U 4K screen and the behaviour was once again the same and reproductible (4K 30Hz unless using the double cable connection trick - with as major difference that the dock was unable to reproduce anything through the HDMI port, only DP was working properly - HDMI being needed here only to reach 4k 60Hz - so there's another issue where hdmi output is not working for some screens)

Therefore it must be linked somewhere to the ability of the dock to communicate at the right speed with video output. I passed all the details of these tests to Dell support already.

@Duschnouk  Great data points! Hopefully it helps identify underlying cause and a fix that doesn’t take too long to get released!

@DELL-Chris M  In addition to the other threads I linked in my earlier post here, this one relates to an Inspiron 7706 and a WD19 exhibiting the same problem of HBR3 support on the source system and yet inability to run 4K 60 Hz. That user however confirmed that they COULD run 4K 60 Hz through a Dell DA300. The DA300 and WD19 should have identical single display output capabilities, so this further suggests that the WD19 is to blame here.

So altogether there are now reports of this problem condition involving four different system models, the WD19/WD19S, and multiple display outputs and displays.

Any news here? I have 5420 with 10th gen, but support didnt solve this issue right imo. 

Hey, I have the same issue but can contribute some important detail.  I have a Samsung Space 4K monitor connected to the WD19 dock, and my work computer is a Latitude 7520 laptop.  I too can only reach 30 Hz both on HDMI or DP.

The interesting thing is I also have an Alienware X17, which I can connect instead of the Latitude and it does get 60 Hz, same dock, same cable, same monitor.  The problem clearly is the 7520.

Oh, and one more bit of info I forgot.  I have the WD19 at home, however at my office I have a ThinkPad USB-C dock connected to a very similar Samsung 4K monitor.  When I take my Latitude 7520 to the office and connect it to the ThinkPad dock, it DOES get 4K @ 60 Hz. 
So now that I think about it, the issue is not so clearly the Latitude, it's only the Latitude paired with a WD19. Pretty weird.

Saw this thread and thought I should mention that I also have the WD19 4k 30Hz limitation on my HBR3 system as detailed here :

Silver Inspiron 7506 -> WD19 -> S2721QS = 4k 30Hz

edit: I know it isn't a Latitude, but figure it is relevant to this thread.

See: https://www.dell.com/community/Latitude/Latitude-7420-w-LG-27UL850-monitor-WD19S-dock-4k-Only-30hz-but/m-p/8327882/highlight/true#M47154

guys, i have the same problem with my Latitude 7320 (and another 13th gen latitude 7000 series) and WD19DCS, basically not able to get 5K 60hz, only 30hz. i have updated drivers and bios of dock and laptop. any suggestion on what's next?

ironically, a 13th gen HP dragonfly with the WD19DCS dock can do 5K 60hz....how weird is that?