As mentioned last week, we’ll cover the new progression system coming to PAYDAY 3 in the next game update. We’ve spoken on it in loose terms before, but the current challenge system is being removed from the game to make way for the new system.
That being said, I think you'll find that the compensation (as you can see below) for the removal of Challenges should create a more consistent progression, and less about big spikes.
You can read the full blog here: https://t.paydaythegame.com/c/ph2ffp
