This subject has been widely discussed here: the limitations of Sonar regarding the use of videos.
What I can not accept is how these problems were not resolved after so many years.
Maybe because most users do not work with videos. 
But still, many users work with videos every day, including me. I often receive MP4 files as work material.
Some people may say that Sonar is not a video editor. I agree! And it should not be. But Sonar should at least be good at least playing the videos.
But not.
Today I'm forced to work in parallel with Adobe Premiere because:

1. Sonar is too slow to play a project when I specify Trim-in time. The further forward, the longer it takes to start play. This makes its use impracticable. The odd thing is that if I do not set the trim-in time, Sonar plays the project quickly anywhere.
2. HMFS placement is inaccurate. For example, in a project with timecode at 24 FPS, using a video that shows its own timecode, the Sonar timecode almost never matches the video timecode. Sometimes Sonar shows a frame forward or one back, rarely shows the correct frame.
3. Still in the example above, the MP4 videos I get have exactly 5 seconds of title and technical details, and the video timecode starts at zero from 5 seconds. If I set trim-in time at 00:00:05:00, Sonar shows my original video timecode sometimes at 00:00:00:03, sometimes at 00:00:00:05. 

The problems above never happen in Adobe Premiere. And again, I do not want Sonar to be a video editor, but at least make it easy to play videos correctly.

Ive worked with Sonar and videos for years(1992??).  Sonar has gotten way better.  I have always prepared the videos from clients before I start work.  I always create a 10 sec roll up, create streamers to visually tell me when music starts/stops/changes and burn my own time code just for safety.  The small amount of time I spend before hand pays off dividends later in the work process. I have been making my Sonar pic files AVI and have been happy with the way it works.
 
As far as correct time code, being a frame or 2 off here and there is going to happen no matter what software you are using.  Computers don't actually use frames anymore and where one frame starts and the other stops is going to vary.
 
Sonar does have its quirks, but the way it handles softsynths, work flow and the speed of mix down far outweighs the video issues...which I allow my video program to handle for me.

Yes, there are several ways to get around these issues, and I also have my ways.
But the correct thing would be for the problems to be solved.

just checking...are you changing your clock settings in preferences to match time code?
 
so my clock in Sonar always has an offset of :00:59:50:00 and I know that picture is going to start
at exactly :01:00:00:00....but I have to know what the video frame rate is and match it in Sonar.
 
TV Shows tend to be at 29.97 drop frame.  Commercials and other stuff tend to use Non-drop frame settings.  Films are in the 23 or 24 fps area
 

Jimbo 88
just checking...are you changing your clock settings in preferences to match time code?

Sure.