Oh, that's actually quite easy, I'd think.
They are on a hostile planet. A death world, nearly, where damn near everything is trying to kill you, and it's a five year journey back home. They just need to preemptively lock up any liabilities and dump them in the deep forest with no communicators or even clothes.
Of course, that doesn't make it foolproof.
The pilot that switched sides for example, that was something no one had any way of preventing without prior knowledge
and of course they could use communicators to get the word out to Earth. But whilst the first can't be guarded against, the second can. In terms of suppressing the scientists, they really had a wealth of options,all of which involve the 'tragic' death of several members of the science team after they went rouge, stole a transport and crashed in the deep jungle despite valiant attempts to save them.
It
could spiral out of control rapidly. But with the proper precautions, it probably won't. Admittedly the death of most of the science team would raise eyebrows, but I think they could deal with that.
EDIT: This doesn't take into account things like people balking at the very idea, like the CEO might. I'm just musing, you understand.