Again - vst-instruments are totally interchanged

v2017.03
For a few days I had the problem, that after a "Rescan" of the vst-plugins all my simple-instrument-tracks are assigned to the false synthesizers and instruments. But now I see, the problem has a different cause.
It is because I enabled (at the same time) external MIDI-Outputs to external synthesizers.
- Novation Bass Station
- Roland Integra 7

And now all simple-instruments are again routed to an other plugin and to an other track.

For example:
When I solo Track 7 (AKAI VIP - vst-synthesizers), it plays the notes from track 9.  ! No Joke !
And when I click on the keyboard-icon (in the track-view) it opens "Kontakt" istead the AKAI-plugin.
But what I hear is the AKAI VIP synthesizer - not the Kontakt - with the notes from the false track.
When I select other extern MIDI-Outputs and MIDI-Inputs I get again a different assigment.

That is no joke.

Is there anyone else who has the same problem ?
Is the problem only with the simple-instruments?
Is the problem the order of MIDI-out and MIDI-in ?
How can I prevent this?

The audio-tracks and all other vst-plugins are also intact.
Older projects from 2016, 2015 and older open with the right instrument-plugins at the right place with the right midi-track.
Affected are my 2 projects that I startet with v2017.03 or 2017.02 (I'm not sure)
 

Do you mean, when you select Insert>Soft Synth>'Whatever synth'>Simple Instrument tracks you get 'totally different synth'. Then yeah I've had this this month. I had made my own custom Plug In Layout for synths, and it was all screwed up.
 
I set it back to the Sonar default categories of Sort by Category/Manufacturer/Type, and it was fine.
 
I had planned on making a new layout, but after seeing your post and checking , it's working fine again. Maybe try the other plug in Layout choices for a bit, of make you own layout fr a bit.

It happened as I enabled two MIDI-out and MIDI-in to extern synthesizers. At this moment no project was opened.
As I openend a project, where I just worked 15 minutes before, all simple-instrument-tracks are assigned to other midi-tracks and vst-instruments.
I try to reproduce it in a new project.
 

"... enabled two MIDI-out and MIDI-in to extern synthesizers ..." Do you mean in Edit->Preferences MIDI devices or MIDI instruments, or do you mean enable input echo on tracks, or ???

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.