The game freezes the moment I defeat the Sigma Stage 1 boss, making it impossible to progress any further.
I experienced the freeze both when using the secret weapon I obtained and when defeating the boss with normal weapons.
After force-closing the game and loading my save again, my chip count was reset to 0. Fortunately, the secret weapon capsule can appear again after meeting its unlock condition again, so I was able to obtain the secret weapon once more.
I was playing version 1.00.3.