It looks like the VideoEngine variable in AUD.ini was changed from the default value 1 to 0 in X3. This causes SONAR to use the old DirectShow engine engine. The new SONAR is running the default Media Foundation engine. The new media engine was introduced in X3d. In addition to the documentation, there are several articles about the change:
https://www.cakewalk.com/Support/Knowledge-Base/2007013355/SONAR-X3d-Update
https://www.cakewalk.com/Support/Knowledge-Base/2007013354/SONAR-X3d-Switching-between-Media-Foundation-and-DirectShow-Video-Engines
https://www.cakewalk.com/Support/Knowledge-Base/2007013353/SONAR-X3d-Launch-Error-for-Missing-MF-dll
 

mdages
wtf, I wrote a larger post, preview it and after submit it was gone away. very frustrating.

The posts were blocked by the automatic anti-spam software. Send a PM to a forum host with a link to the thread and the post will be restored

@Scook
 
I'll give this value in aud.ini a try and report results when I'm back in studio.
 
regarding the forum message:
I didn't see any message or notification from the forum software. Something went wrong when I put in picture links in my message. But I didn't see the reason. After submitting nothing appears, no message, no error, no post.
 

Yes, I forgot, the spam blocker just refuses to post the message or deletes after posting without notice. This usually happens when the spam blocker detects what it considers an issue with a link in a message. A PM to a host to get the message back.

Thanks @scook .
 
It seems that you're correct regarding the VideoEngine variable.
In my Sonar X3 installation the value is 0 and in Sonar-2015 there is no such a value in the aud.ini.
I've added:
 
[Video]
VideoEngine=0
 
to the aud.ini of Sonar-2015 and now it works without delay on playback and all the options for setting render quality are back.
 
Hmm, but this means to me, that the old DirectShow VideoEngine runs better and faster as the new one.
 
Would be fine if Cakewalk could do further improvements for video support in upcoming updates.
 
regards
Markus

Noel's most recent comments about video updates http://forum.cakewalk.com/FindPost/3145599
 

There are something like 8 posts that the anti-spam filter nuked. I think they're all the same but am not sure. I can restore them if you can give me some guidance as to which of the eight need to be restored. 
 
It's a bummer when this happens, but Akismet is pretty good about "learning." After I restore a couple of your posts, it will put you in the "good guy, don't hassle" part of its little brain.

I restored the unique posts. Once restored, it was easy to see this was a configuration issue. X3 is set to the old video engine and the new SONAR was using the new engine. In this case SONAR needs to be set to the old video engine.