I think yes because 3PO is technically an evade, but am not sure.

Anyone know?

The exact timing for Crackshot isn't clear since the new rulebook came out.

see here:

https://community.fantasyflightgames.com/topic/185791-crackshot/

However whatever the timing window might be (modify defence dice or compare results) since a correct guess with C-3PO adds an evade result to your dice pool before the Modify Defence Dice step, you could use Crackshot to cancel the evade result that he generates