Replacing the hammer solenoid end cap is pretty straightforward - I did it the same way Phoenix Typewriter did. You always learn from the experts :)
Unfortunately, it wasn't the end of this machine's problems. The ribbon cassette didn't want to fully descend into the working position, no characters were printed though I saw their dry impressions on paper. The fix was very simple, as it turned out (shown in the next part), but at the moment I was filming it, I didn't have that idea yet. I decided to cut it pretty short and do some research off the camera, and I also went through the tedious process of cleaning the enclosure.

My (pretty short) repair video:

PhoenixTypewriter's video: