Hi, Same problem here, I'm using a simple USB-C to DisplayPort cable without brand, that was working fine in the last years.
With the last update 10.15.4 all time when i try to take up the laptop from sleep, i need to unplug and plug the cable several times, till the macbook flash the screen and pass though the image to my ASUS PB278 monitor.
After do the SMC reset just get worst, now even reboot the macOS with the lid closed, i need to open the lid a close several times.
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Another problem also after the update with a dock station from UGREEN (HDMI, VGA, Ethernet, 3 USB-A, microSD and SD reader), also i need to unplug several times till works.
Also the laptop don't wake up from sleep when i press a key in the keyboard connected over USB in this dock station, or a USB mouse.
I'm using a MacBook Pro 13 mid 2017 with 2 Thunderbolt 3 ports.