Now Time Stutter and Hang

I'm sure I've seen posts about this but can't find them.  Please redirect me.
 
For the most part the only midi I use any more is Superior 2 but for this song I have brought a midi piano part in from BIAB and after I've comped a final part together I'm getting the Now Time Marker stutter and hang issue.  The song will play to about ± 3 minutes and the it starts.  First stuttering and then hanging as the song continues to play.  I've even had the keyboard and mouse cease to work!
 
I'm pretty sure it's related to this midi file as I can open other projects and they play through fine.  I've tried playing the midi file through the TTS-1 and the True Pianos Amber, (I've never used Amber before, maybe I'm missing something), but it makes no difference.
 
I have been having other Sonar problems over the last several months but this is different.  I will continue to search for answers but anything you fine folks could suggest would be greatly appreciated.
 
Thanks.
 
Platinum Newburyport

Have you increased the MIDI buffer option "prepare using milliseconds" ?
AFAIK this prevents MIDI dropouts only but you should increase it no matter what.
I set it to 1000 and then forget it.
Somewhere in Platinum it was defaulted to a ridiculously small value (250?) so if you clean install Plat, it reverts to the default.

microapp
Have you increased the MIDI buffer option "prepare using milliseconds" ?
AFAIK this prevents MIDI dropouts only but you should increase it no matter what.
I set it to 1000 and then forget it.
Somewhere in Platinum it was defaulted to a ridiculously small value (250?) so if you clean install Plat, it reverts to the default.

Thanks for that.  I'm going to take a look at those buffers again.
 
I've edited my second post to clarify that the stuttering begins in the time line prior to the actual tempo change, (in the time line), not before I added the tempo change.  Once I remove the tempo change, the Now Time marker works as it should, no stuttering or hanging.

Just as a follow up to this problem, I can't find a buffer setting that fixed this.  The only solution was to delete the tempo changes.  I was able to render the last few bars of the midi piano part and working against that, I can stretch the midi clip to match the tempo change. 
 
I didn't explore this but I think the problem might be the way I created the tempo changes.  I had significant changes in tempo over a measure or two using the "Straight Line' tool.  This creates hundreds of very small changes and maybe the GUI can't keep up.  As I mentioned before, the audio and midi continued to play just fine.  The time line and other aspects of the interface slowed down or stopped functioning.
 
Anyway, that's where this is at present.  Thanks again for the suggestions.
 
Paul