fwiw I experienced the same problem and solution, but it took some time for me to find this thread. Thanks for the troubleshooting-seems like a problem that might need to be addressed in a version update!
It is not a bug in Dorico but in the new MIDI stack in Windows that people are getting as part of the updates. When using WinRT MIDI it gets the timestamps wrong and wants to trigger your notes to play 3 years in the future instead of now.
Hopefully a reboot will clear the notes, to avoid the problem of getting to year 2029 or something and your computer starts playing notes that you played on the keyboard years before and never heard, an unintentional MIDI time capsule. That would be very confusing.