Here’s a simple explanation: MYE89
Start a game and press the interact key. You’ll change into Bastion but will not automatically start his ultimate.
Then, change the game mode to skirmish and start another game. When you press the interact key, you will change into Bastion and his ult will automatically start.
Lastly, change the gamemode back to deathmatch and in the “ENTER” rule, change the wait time in the second to last action to 1 second. This time when you press interact, you will turn into Bastion and automatically start.
So apparently in specifically deathmatch you have to wait at least a second to use the “press button” action after force swapping a players hero. Seems weird to me. I have tested this with a few different modes, and deathmatch / TDM are the only modes where this happens.
EDIT: the “press button” action isn’t the only one that works weirdly in deathmatch, there seem to be quite a few. This is just an example of one of them.