Operating system: WIN10 PRO x64
Graphics card: NVIDIA GeForce GTX 960
Processor: AMD FX-8320E Eight-Core Processor
Broken: 2.80 #d140e597a6a8
Short description of error
Suddenly, I don't know when, I only realized it when i was trying to render, the render engine changed to cycles.
I have no clue how this could happen, but when trying to change the engine back to cycles, it didn't show up in the dropdown menu.
Then I decided to change the engine manually via blender console command. The error message said me, that cycles isn't in the render engine enum.
After restarting blender everything worked well.