I believe I've read reports about solo track failing to mute other tracks, but couldn't find them with a quick search.    Here's a screen capture showing, first, tracks solo'd and tracks muted, and then, unmuting some of the tracks while leaving the original solo tracks as solo.   No audio with the video here, but you can see the activity meters flickering, and the sound comes from the violin tracks -- not muted, not solo'd.      Ideas about how to fix this?   
 
https://vimeo.com/184837138/b327e205c9

No buses solo'ed?

Hello,
Any sends enabled unseen.
MJ

Checking all that now.    Just did a fast bounce, for the selected and solo'd tracks --- the output is correct.   When I play the same selected and solo'd tracks, sound from the other tracks is heard.

So:  yes, it was caused by a send; bypassing the send on the NOT SOLO track caused the extra sounds to stop.   Also ticking the "post" button, so it is ON (blue) -- that stopped the extra sounds too.  
 
Something not right.    I'm using Virtual Sound Stage as a plugin on the aux bus referenced by the sounding but unwanted track.   ... will try changing to another VST reverb.   (edit) same problem with BREVERB.