I have noticed that Dorico sends Note ON/Off commands before sending CC change commands (attached is a picture of the MIDI Monitor on Kontakt)
In this example I have the Playback Technique patch change set to CC 3, Value 2
This creates an issue when your VST uses CC commands to change patches, as in my case when a Note On command is sent, then the Program Change is made throgh a CC (through a multiscript). As a result the Note OFF command goes to the wrong patch, leaving the first patch “hanging” and not triggering the correct patch until the next “Note On” Command.
For now it seems the only way to change patches through Midi Commands would be Keyswitching “Note On/Off” as CC shows up too late.
In order for patch switching to be of any use, all commands set in the Expression Maps should happen before the first “Note On” command of the actual music/midi.