I can't believe I haven't noticed this before, but I guess that's why it hasn't been fixed... not enough people encountering it frequently enough. This appears to go back to X1 so I'm guessing there are multiple reports out there already, but can someone confirm?
 
- Select clips in more than one track, and set the Now time late rin the project.
- Edit > Paste Special, check the Paste to One Track option, and OK.
- Verify both clips paste to the focused track.
- Move the Now time and choose Edit > Paste Special again.
- Note that the Paste to One Track option is unchecked, and OK.
 
Expected Result:
- The clips are pasted to their respective tracks.
- Choosing the Paste to One Track behavior either persists with the option remaining checked in the dialog, or works only once and is automatically cleared (Pre-X1 behavior).
 
Actual Result:
- The paste to One Track behavior persists indefinitely though the checkbox is cleared, including in new projects after closing and re-launching SONAR.
- Toggling the Paste to One Track option on and off in the Paste Special dialog is necessary to reset it.
 
 

I'll confess to never using the option so I may have steps wrong. I could not replicate the problem. Here is what I did and the result:
1) Created three tracks with one clip in each. None of the clips overlapped on the timeline
2) Lassoed the clips in the first 2 tracks
3) Did Edit > Copy
4) Gave third track focus
5) Moved Now time past the end of the clip in the third track
6) Did Edit > Paste Special with "Paste to One Track" enabled
result the 2 clips from tracks 1 and 2 pasted into track 3
 
7) Moved Now time to the end of the project
8) Gave first track focus
9) Called Edit > Paste Special
result the "Paste to One Track" is still enabled from the previous paste and clicking OK pasted the the 2 clips from tracks 1 and 2 into track 1
 
10) Moved Now time to the end of the project
11) Did Edit > Paste Special disable "Paste to One Track" (which was still enabled from previous pastes)
result the 2 clips from tracks 1 and 2 pasted into tracks 1 and 2

So you're seeing a check mark in Paste to One Track every time you open the Paste Special dialog? I not longer see the checkmark, but the behavior persists. In 8.5 and earlier, both the checkmark and the behavior are cleared after the first paste.

Yes, once I check the option "Paste to One Track", both the check mark and behavior persist in the session until unchecked. I too am running Win7 64bit BTW. I have performed the test several times in several sessions starting with the same empty project.

Okay. Thanks. That's kind of what I would have expected. So apparently I just have some display issue with the checkbox in the dialog.