Jora puts on his mask twice.
Night was obviously filmed at day.
In the early extended work-print version Andriy, as well as many other actors quite obviously watching at the camera many times. It was corrected in the final theatrical version.
If you look closely, NTNTN channel logo remains one frame more after channel is switched to white noise.
Sometimes laugh and voices heard in the background, indicating crew presence.
While Jora drinking tea outdoors with two Sergeys, some of the props and equipment (such as soap bubbles equipment used for hallucination sequences) can be spot in the background.