Damon777, has the Tempo function actually changed? AFAIK, there has never been an "Delete existing tempo changes" -kind of feature in SONAR (that would be great to have!) for changing the project tempo. SONAR assumes the changes in the middle of the project are there for a purpose, and are not meant to be changed even when original tempo is changed.
The two usual traps people fall into:
-The project has copy-pasted MIDI-clips. Each of them has a tempo definition in the beginning. Numerous times
during the years I've had to go through the clips/Tempo view to delete those. I don't remember if there's a "Paste Special" -option for not pasting tempo changes, maybe there is and I haven't noticed??
- You have tested different tempos somewhere in the middle of the project and so inserted tempo changes.