Error initializing CoreMIDI

How to solve this annoying error message and MIDI failure on startup of Logic Pro X?

I've had this error message popping at launch for months. Now it's getting worse and requires several restarts before the MIDI is activated.

I've checked the forums and followed many tips but to no avail;

1. Changed the sequence of switching on the connected sound card and MIDI keyboard
2. Gone to Library/Audio/MIDI Drivers and removed any un-necessary elements (actually, the folder is empty!?)
3. Updated the software for Logic X and connected components

My gear;

Mac (Retina 5K, 27-inch, Late 2014)

4 GHz Intel Core i7

32 GB 1600 MHz DDR3

Sound card;

UA Apollo Twin - DUO Thunderbolt

Keyboard;

Korg PA900