Ultracold polar molecules with fully controlled internal and external degrees of freedom have applications in diverse fields including ultracold chemistry, strongly correlated many-body physics, quantum information, etc. Recent experiments with two-body reactive molecules have confirmed that chemical reactions can still happen at ultracold temperatures with rates dominated by the quantum behavior of the collision partners. In this talk, I will report our recent results in creating and studying an optically trapped gas of ground-state ultracold bosonic NaRb molecules with controlled inelastic loss channels and chemical reactivates. We show that rapid loss of molecules persists, contrary to intuitive expectations, regardless of the two-body chemical reactivity. Our investigation also provides strong evidences that collision complexes are playing the key role in understanding the observed losses.