Precision 5510 display resulution on external monitor incorrect

I have 2 Precision 5510 laptops that are identical in hardware. When I hook up one to an external monitor (Seiki SE39UY04) via HDMI the resulution is good (3840x2160 and looks like it). However, when I hook up the other laptop to the same external monitor the resultion is listed as 3840x2160 but it looks more like 800x600.

I've compared all the settings I can find between the two laptops and they all appear to be the same. Resulution, refresh rate, etc. Both systems have the same hardware (Intel HD Graphics 530 and NVIDIA Quadro M1000M) and are running the same driver versions. I've applied all available hardware/software updates from Dell.

Does anyone have any ideas why one laptop works properly and the other does not?