Reproduction steps:
1. Open attached Unity project.
2. Open and play "Exe's > MouseFlightScene" scene.
3. Move mouse around and notice how game objects on the screen moves(GIFs attached).

Additional notes:

• Script, that is responsible for it is called "Scripts > SwivelGuns"
• In 5.4.0a6 objects twitches instead of moving into opposite direction.
• Now the strangest part: twitching in 5.4.0a6 is possible to workaround by uncommenting "print" parts in the "SwivelGuns" script (there is no single responsible "print", it looks like certain amount of them has to be uncommented to work).
• Uncomment line 66 and line 105 in the "SwivelGuns" script to see x and y values in real time when scene is played

Reproduced on: 5.4.0b1
Not reproducible with: 5.4.0a6