Symptoms
This is happening during workflow design (in K2 Studio/K2 Designer for Visual Studio). When clicked on Finish button after make some changes to Email Event, the CPU usage will shoot up and the K2 Studio will not responding.
This might persists up to 30s depending on the machine capabilities.
Diagnoses
We able to repro the same behavior from our end as well.
Resolution
Logged as issue to be fixed in future release but there is a coldfix for this. Get it from K2 Support.