(Already reported in Reaper forums)
Hi,
I noticed a bug while using Reaper 7.07 + VST3i: Synthesizer V Studio Plugin (Dreamtonics Co., Ltd.) (32 out).
It is very easy to reproduce:
-New Reaper project.
-Add a track.
-Add plugin (normal VST3i, not ARA)
→ VST3i: Synthesizer V Studio Plugin (Dreamtonics Co., Ltd.) (32 out)
-Define a “selection” on the main time ruler (say the first 4 bars, it does not matter)
-Remove selection at any stage of the project (press “ESC”). Or define a new one without moving the handles at the ends of the selection.
At this moment Reaper crashes, does not need anything else to crash.
Of course I noticed the problem in a real project with a few tracks, MIDI clips, a few Kontakt instances and Synthesizer-V with real melodies and lyrics inside, etc. But it happens exactly the same with an empty project as described above (the file is just 6.2 KB).
Just open the empty file with 1 track and Synth-V and a time selection, press “ESC” and Reaper crashes.
This does not happen with dozens of plugins I’ve used in Reaper for years, it is just Synth-V
Running the plugin in dedicated / separate process does not help, same exact behaviour. Apparently there is a bad interaction between Reaper and Synthesizer-V.
I am using the latest beta (only choice for projects in Spanish language) and under W10.
Did anybody notice it?
If I am careful not to remove the time selection in Reaper, I can complete the project (it was a funny tune with 5 voices), no issues, everything worked as expected. Synth-V is getting better every day! 
Regards.