Engine from source - Bad image error - how to determine exact error?

Hello!
Frustrating issue really.

I’ve built engine from source. it worked fine.
But then, after a few corrections, it was built without any errors,
but refuses to launch with
“UE4Editor - Bad Image”.

If I made mistakes in code - then why it compiled without any errors?
If not - then what is going on?
How to cure it?