Howdy MG,

I'm pretty certain that the problems you're observing with the tempo can be pinned down to less-than-optimal feedback and default values in the Tempo dialog.

Here's what I see:

If I don't have a region selected and I open the Tempo Dialog at any point after stopping playback, the dialog shows me the following:

(1) the Tempo value at the very beginning of the file (not where the green Playback cursor has stopped)
(2) the Region (in the lowest part of the dialog) fields have the settings for the entire song, rather than beginning where the green Playback cursor is set.

Going further,
(3) if I click "Cancel" after looking at the dialog, the tempo changes in the file remain unchanged.
(4) IF, however, I click "Ok" rather than "Cancel" after viewing the dialog (without purposely making any changes in the dialog) then the Constant tempo value that was showing is applied to the entire song (which was the default Region in the dialog.)

It's definitely tricky (and dangerous) that the setting of the Tempo dialog can change your tempo adjustments without you explicitly changing anything in the dialog. I'll report this problem to Mark for fixing.

Thanks for reporting the problem!
Sherry