Logic CPU overload with midi controller
I'm having a problem wherein my midi controller keyboard seems to cause Logic to suck up the entire CPU, making getting anything done next to impossible. Now, this only happens when the controller is powered on (it's a Nektar Impact LX61+, if that makes a difference). My audio interface doesn't cause this problem at all when it's connected, and the problem goes away immediately once I disconnect the keyboard. This is incredibly annoying, and I'm hoping someone has some insight as to what might be going on, although I've seen dozens of threads discussing Logic sucking up CPU that go back several years, and I haven't seen a fix. 
It's important to note that this problem happens whether I'm in a project with dozens of patches loaded or in a brand new empty project after a fresh restart, so I don't believe that is related. As well, before I acquired the LX61+, I was controlling midi just using a microKorg XL, and I never had these issues. Although I should also note that the LX61+ did not begin causing this issue until I had been using it for a couple hours. But it's been consistently doing this since the first time it happened.
Here are some of the troubleshooting steps I've already tried, none of which seemed to have any effect at all:
- Re-installed Logic and drivers
- The controller is powered by USB bus, so I purchased a powered hub
- Tried a different USB cable
- Tried fresh project
- Loaded Logic and the controller on a different, brand new computer (2016 MBP, 16 gigs ram, SSD), exactly the same performance issues
- Tried the keyboard's low power mode
- Increased I/O buffer size in Logic
- Rebuilt defaults in the Control Surfaces menu
Am I missing something glaringly obvious that will make me feel like an idiot as soon as I read it?
MacBook Pro, OS X El Capitan (10.11.6)