Hi,
OK with a working input I was able to get VSTHost crashing. And it’s the same as with Mixcraft. It is calling the IEditController from the audio thread :
> again.vst3!Steinberg::Vst::AGainController::setParamNormalized(unsigned long tag, double value) Line 308 C++
vsthost.exe!CVST3PlugIn::DoProcess(long) Unknown
vsthost.exe!CSpecVst3PlugIn::ProcessReplacing(float * *,float * *,long) Unknown
vsthost.exe!CSpecPlugIF::ProcessReplacing(long) Unknown
vsthost.exe!CSpecPlugIF::ProcessAudio(int,bool) Unknown
vsthost.exe!CSpecPlugInHost::PassThruPlugIn(class CSpecPlugIF *,bool,bool) Unknown
vsthost.exe!CSpecPlugInHost::PassThruPlugIn(class CSpecPlugIF *,bool,bool) Unknown
vsthost.exe!CSpecPlugInHost::PassThruPlugIns(bool) Unknown
vsthost.exe!CSpecPlugInHost::OnSamples(float * *,int,int,unsigned long) Unknown
vsthost.exe!CWorkThread::OnEvent(void) Unknown
vsthost.exe!CBackgroundThread::GetEvent(unsigned long) Unknown
vsthost.exe!CBackgroundThread::RunThread(void) Unknown
vsthost.exe!CWorkThread::RunThread(void) Unknown
vsthost.exe!CBackgroundThread::EvtThreadProc(void *) Unknown
vsthost.exe!_AfxThreadEntry(void *) Unknown
vsthost.exe!_endthreadex() Unknown
vsthost.exe!_endthreadex() Unknown
kernel32.dll!00007fffaabe3034() Unknown
ntdll.dll!00007fffad2a3691() Unknown
Please report this issues to the host developers. We try to do the same 
Cheers,
Arne