If they were happy with Mateo/Urias on the left side, then they could have just let Henderson play 2B. But they decided they needed Frazier and now it's tough to take Urias and or Mateo's glove out.
Some of these defensive issues are also because they moved Henderson around with Westburg defensively in the minors because they want flexibility. I get that, but with your top guys, you need to decided where they are going to play and mainly play them there.
They've never really had a plan defensively for Gunnar besides SS and 3B.