UltraSlim Docking Station 2013 won't put DisplayPort connected monitor to sleep

[exT613]

I have 2 monitors connected to my HP UltraSlim docking station 2013, 1 is using VGA cable and the other using 1 of the 2 DisplayPort connections. When my laptop puts the monitors to sleep due to inactivity, the VGA monitor goes into sleep mode ok but the monitor on the DisplayPort blinks on and off forever and never goes to sleep. The message that blinks on the screen is "no dp signal from your device". I tried the other DisplayPort output on the dock and same thing happens. I tried the DisplayPort on the Laptop itself and it went into sleep mode ok. I tried updating the display drivers on the laptop and the firmware on the dock and same thing still happens. I also tried an older model docking station that has only 1 DisplayPort output and the monitor goes to sleep ok. So I'm convinced it's this 2 DisplayPort output docking station at fault, but I need to know if it's a software defect that will be fixed, or if the hardware is defective so I can return it to the vendor.

Docking Station model: D9Y32AA#ABA (Firmware: 2.33.004)

Laptop Model: HP EliteBook Folio 9480m

Monitor: Dell P2419H

OS: Win 10 64-bit

[exT613]

I found this post that seems to have the same issue: https://community.spiceworks.com/topic/2035617-screens-keep-waking-then-sleeping-rinse-repeat

However the response from HP seems to suggest that the issue is fixed in firmware 2.33.000 and I'm running a newer firmware than that. So the problem has perhaps returned due to further Windows updates. Can someone from HP Support please respond?

TITLE:  HP Ultraslim Docking Station DisplayPort (DP) Hub Firmware
► Ver. 2.33.000 Rev. A, 1 January 2017, sp79015.exe
http://ftp.hp.com/pub/softpaq/sp79001-79500/sp79015.exe

SUPERSEDES:
Ver. 2.30.000, Rev. A, Pass: 1, 18 April 2016, sp75855.exe

FIXES:
- Fixes an issue on the display of a DP monitor connected to the system using the docking station which causes the display to flicker when the docking station DP monitor is set to low power mode.