Hi James,
Thanks for the response.
All of the displays are connected via the dock [HP NZ223AA], with the exception being the bottom middle display (which connects via the HP EliteBook 8760W's onboard DisplayPort).
Unfortunately, I can't access the HP EliteBook 8760W until later this evening. However, I've done some testing with the two dysfunctional HP NL571AA adapters on another computer (running Windows 8.1), with varying results. The first adapter is recognised correctly by the device manager, but is unable to detect when a display is present (i.e. plugged in). The second adapter results in the following errors:
The third adapter appears to work fine. Would it be safe to assume that two of the HP NL571AA adapters are faulty and would need replacement?