Hi Lucky!
Sorry for the quantity and volume of bugs you encountered with the build you played (0.6.9), introducing a new playable character introduced more bugs than we anticipated.
Fortunately, most of these issues have been fixed as of 0.7.1. There is still some known performance issues with the stages, but enemies now unload from the camera when off-screen and their AI calls have been greatly reduced per second. These boosts are most noticeable on the debug stage.
We are making sure to clean up remaining legacy bugs before adding major new features to the game, it is the goal of our January sprint!