Ever since I started using it, the j5create USB to HDMI monitor adaptor has given me some form of grief. Don't get me wrong, having a 3rd screen on a Mac Mini is great, but it comes at a cost.
Uncheck "When switching to an application, switch to a Space with open windows for the application".
I'm unsure if this has any negative effects to the system as I've only had to use it once since implementing it. If there's a better way please get in contact with me.