I mean "Edit->Preferences MIDI devices". The two added MIDI devices are USB-MIDI.
It happens to all vst-synthesizers. They are ALL totally interchanged.
They are Kontakt, EastWest, AKAI-VIP, Addictive Drums, Addictive Keys, Arturia, Cakewalk Session Drummer

It's even that I solo Track 7 and it plays MIDI from Track 9 on the wrong vsti-synthesizer. So the simple instrument in track 7 is assigned to MIDI track 9.
So I guess SONAR has made a total chaos of all midi-tracks and all synthesizers as the order of the devices has changed. This happens in 2 projects I startet with 2017.02 or 2017.03.
Even all my daily backups (over 50 files) load with all instruments interchanged. So this must be up by rearranging the MIDI-devices.
Older projects load with the right instruments at the right place. It must be up by a bug in 2017.02 or 2017.03
 
At the moment I use 2017.04 (early access) and I cann't reproduce this chaos in a new projekt. Only this 2 projects are affected. I worked in this projects for 4 weeks, until I added 2 new MIDI devices.
 
So I make the next days 2 new projects and copy the tracks from the 2 old broken projects. Then I will use no more simple instruments.