Hi…
i’m not an expert on this, but i have been working the past weeks with steppers now, and starting to get something that looks promising 
The difference is that i’m using a stepper driver compared to you.
I also experienced disconnections when running a while loop, and solved it by putting a Blynk.run() inside it. http://community.blynk.cc/t/blynk-run-in-other-loops/1042
I specifically use it to run the motor while pressing a button-widget, and i’m not sure why. but sometimes it get chunky movements. i think it might be because of blynk.run sometimes taking to long due to slow connection.
If your problems isn’t solved, post your code and we can take a look