A VST 3 host has to send all automated parameters to the edit controller. This allows for time-compensating them, so the UI is in sync with what you hear. This can be a value the audio processor processed half a second ago, for example.
Unfortunately, many plugins update their edit controller themselves, so its UI knobs show the values at the time the audio processor processed the data. If the host sends time-compensated values the UI knobs will jump between the processor time and the UI time. This looks bad, so I’m more or less forced to remove the time compensation from my host.
Perhaps it would be a good idea to add a way for the plugin to say “Sorry, I still update the UI myself, please don’t send parameters at all, or at least don’t time-compensate them” or “I do this correctly, please send time-compensated parameter values”?