Just upgraded and did a few tests. It seems there is something wrong in processing VST3 in stand-alone version (working correctly in ARA mode).
How to reproduce :
import a sound
make a square selection
process a VST3 (I have tried several, mainly reverbs)
=> reverb is calculated + some strange spikes appears outside the selection (like a dirac in a delay)
Again no problems in ARA only the selection gives an output.
Can anyone confirm it ?
Are you on macOS or Windows ? Can you list a couple VST3 effects that shows this issue ? Would you be able to also post an audio file which show the issue (before processing, and in PM if your prefer) so I can repro as closely as possible your issue. Thanks !