1) Never back out of a Showdown round once you click on the Play button. Just wait patiently for the wheel to stop spinning and the game will load without a penalty.
2) If someone forfeits to you and you can keep playing then great. Finish it out.
3) If someone forfeits to you BUT the "Cancel/Retry" screen shows up ... NEVER hit the Cancel button. Often hitting the Retry button will also be a complete waste of time and you will be timed out eventually and receive bogeys. The solution seems to be to hard close the App and restart it. You will then have to replay those 3 holes. The game will treat them as not having been played. But you won't get any bogeys. If you hit Cancel you will get 3 bogeys.
4) The only risk to actually getting screwed is if someone forfeits or exits out on the tee box before any shots are hit. But this problem may have been fixed now.
At the risk of stirring up a hornet's nest, I have to add that I think one shouldn't forfeit mid-game unless there really is a very compelling reason. This may only be virtual golf, but it is a game like any other and requires sportsmanship when others are involved. I doubt there would be any current CEOs of major corporations or government leaders playing this game ... so ... just let your opponent finish their game!