Hey, thank you for such a thorough review of our game!
To give some feedback on what you wrote: you can indeed shoot without locking on targets using the minigun. You only have to lock on when you use the missile launcher.
The screen issue you had encountered is a new one. I haven't seen it being one from the playtests we've run, might be a compression issue in the build version.
Once again, thank you for the review and nice words. The game is planned to be developed further in Godot, so be on a lookout for that!