Problems with external monitor lock screen on Fedora 28

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I have an external monitor connected trough MIniDP port and every time I lock my computer, both my Laptop and external display turns off (which it's OK). But after some time (2-5 minutes) my external monitor turns on again, at first it only show a blank screen plus the mouse cursor, then some time later it shows my lock screen image.

Am I missing some configuration to prevent this?

My computer it's a Thinkpad P50 with a Quadro M1000M video card (currently using nvidia drivers v390.59), and Gnome 3.28.2