Select several nodes on canvas, for example Start->Task->End. And try to move the selection in a way that mouse will point on a place where one of a node were placed. All selection will be moved back like this movement is not allowed.

Steps to reproduce
1. Model simple process: Start->Task->End
2. Select all 3 nodes
3. Drag selection by holding Start and move mouse to the position where another node were placed before movement started, for example initial position of End. You can use canvas grid to easier orientation.

Actual Result:
All nodes will be moved back to movement starting position

Expected Result:
All nodes will be moved without any complications.