It is known that if you keep playing in the same room for quite some time, you eventually get a bonus.
Such bonus can be:
- increased Credits
- increased Boxes
- increased Research progress %
Now, I believe the third one is bugged. I am currently researching lv.13 FB-22, with a 1.37% progress after each (1x fuel) mission.
Using (3x fuel) grants me a 4.7% ~ 4.8% progress, but this value does NOT change even if I am using multiple fuel units when there is the increased Research Progress bonus.
The last time I had a 400% Rsch. progress bonus and of course I decided to use 3x fuel. I was expecting at least an overall 750% advance if not even a 1200%, but what I gained in the end was always 4.7%.