external display flickers into black screen with cursor

I have a brand new MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports)

running macOS Mojave 10.14.4 (18E226) with two new DELL P2419HC monitors

The monitors support both HDMI and USB-C connections.

While im working one of my monitors will turn black, with only the cursor appears, Windows are still present and i can minimize and do actions ( without actually seeing the windows. the other monitor connected will still work as well as the macbook built in display.

locking and unlocking the mac will bring back the display.

its not consistent to a specific monitor or connection type i.e HDMI / USB-C

What i tried in order to debug:

1. reinstall the OS
2. switch the USB-C ports ( between the two monitors ) - same display will still "blackout" on the other usb-c port , it changes between the two displays from time to time.
3. reset NVRAM
4. create a new user on the Mac
5. reset power management controller
6. replacing the monitors ( to same make and model )
7. replacing all the cables

Thats it.

no clue on how to solve it, Apple phone support solutions didnt help ( above )

this dosnt happen on the built in mac, only on the external monitors and only on one of them ( sometimes left sometimes right )

help