The W bug on respawn also happen to me.
I made a post about that: Bug on moving forward after respawn (give a like so it stays on more on top of the list :D)
it happened to me on a normal match, so i tested it on hero sandbox
It seems there's a bug on the movement when you press "W" or forward immediately after you respawn (or select hero in SandBox Mode)
How to reproduce it
- Enter Sandbox
- Pick a Hero, and when you pick it press W or forward...