Thanks for getting back to us,and truly sorry for this trouble.
Did you used the cables provided in the package?
What is this monitor output resolution?
Have you try change a high end DP cable to have a check?
Needed mini display port cable (for Macmini) so no appropriate cable included in box
Bought new cable from Amazon and it works fine … until you change the input and then come back to the Macmini https://amzn.eu/d/dlt47W9
Refresh rate is 60 hertz and resultion set to recommended 1920x1080
Hi, from your description and this issues happened seems related to the USB-C to Displayport cable. Since now we not have the testing with this scene and we will try get some this type cables to have a test then update to you.
For now the alternatives is recommend to try use the well-know brand with high quality cable,like Belkin.