In short this is because of the 29.97 fps. That .97 is what’s causing this drop. Unless this material is being produced for TV or has some specific technical requirements, then I suggest you just go with a solid 30fps in the future.
I’ve attached a screenshot of the Timecode FX in Vegas Pro 20 and the Time Format settings for Ruler timecode. I copied your project settings and setting Timecode FX to “Time & Frames” is what introduces the lack of “,29” before 00:00:17:00. If I set it to the SMPTE 29.97 options – it has the “,29” now.
There’s probably some math that explains this difference very clearly, but basically in your case you need to have a matching Time Format in your Project Settings, Ruler, Timecode FX. To edit Ruler timecode – go to 3rd tab of your Project Settings or right click on the time above timeline. If there’s an option with your specific framerate – use that; if not – use Time & Frames.
Actually you can set your Ruler to Absolute Frames and try playing around with switching between 29.97 and 30 fps for your project at different points in the timeline. The values will differ slightly (as they should) and at some point they no longer round to the same value and this difference increases every x frames. This shows the .03 fps difference pretty well. I guess that if you don’t specify the .97 fps value then it rounds some things to 30 fps? I feel like it should be something along those lines and there’s probably a more technical explanation.