This is also new and definitely a bug....    I like to sometimes normalize multiple tracks simultaneously after a tracking session to get consistent levels.   This has always worked fine.   NOW however, when I highlight multiple tracks and normalization completes, data from unrelated tracks end up in the normalized clips so this no longer works properly and I cannot do it. SO example:
 
1) I highlight/select  tracks 1 - 6 in their entirety (for example tom tracks)
2) Run process -> effect -> Normalize
3) Now the tom clips contain guitar track data from tracks below and NOT selected
BUG!!
 

This not the only anomaly.
We digitaze tapes and vinyl und have daily thousend of clips that must be normalized.
We get also clips that are - after normalize - OVER 0dB.
And we get also clips - after normalize - with corrupted audio data.
 
To prevent this, the clips must be selected and right-click "Apply Trimming" befor normalizing.
Maybe this also the reason for you.
But again and again (1 time a week) there are cases with corupted audiodata and levels > 0dB.
In most cases we pan-normalize the audiofolder outside of SONAR with Wavelab. Because SONAR has no pan-normalize.

Hi...   This needs to be fixed by Sonar!!!!!   Thanks for the tip!! I'll try the apply trimming