Looks like something broken in Vegas 15 related to video levels while rendering with Sony AVC encoder.
Video from Panasonic X920 camcorder. Media info:

ID                                       : 4113 (0x1011)

Menu ID                                  : 1 (0x1)
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.2
Format settings                          : CABAC / 2 Ref Frames
Format settings, CABAC                   : Yes
Format settings, RefFrames               : 2 frames
Format settings, GOP                     : M=3, N=30
Codec ID                                 : 27
Duration                                 : 7 s 975 ms
Bit rate mode                            : Variable
Bit rate                                 : 23.3 Mb/s
Maximum bit rate                         : 25.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 59.940 (60000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.187
Stream size                              : 22.1 MiB (94%)

I created a new project "V13", in Vegas 13, dragged to the project a single video file, matched project property to video property then changed pixel format to 32-bit (video level) and rendered it with Sony AVC. All good, in player resulting video looks exactly as original video (screenshot attached).

Created a copy of the project file in explorer as "V15", opened it in Vegas 15, pressed Ctrl + S to converted to Vegas 15 format, then rendered it with Sony AVC encoder. Fail: resulting video looks like someone added Computer RGB to Studio RGB conversion before rendering.

At the beginning I tried to create Vegas 15 project from the scratch with the same results. Only then I decided to open the project created in Vegas 13 to be sure that they are exactly the same.

Previews and scopes looks exactly the same in Vegas 13 and Vegas 15.

Then I created a new project, dropped original and two resulted videos on separate tracks and clicking solo button per track one by one. Scopes for original video looks like Vegas 13 Sony AVC rendered video, scopes for Vegas 15 Sony AVC rendered video looked squashed (as after "Computer RGB to Studio RGB" conversion). Added Levels with preset "Studio RGB to Computer RGB" to the Vegas 15 rendered video -- voila, scopes are as they should be.

I tried to render videos with Vegas 13 Mainconcept AVC and Vegas 15 Magix AVC encoders -- everything is OK.

So my questions:

- Is it known bug?

- If it is know bug, are there ETA for bug fix?

- If not, should I create bug report somewhere or this does not change anything? (I have experience with sending bug reports related to previous Vegas versions to Sony. They have not done anything about bugs I sent them...)

- Are there any workaround (other than not to use Sony AVC encoder)?

Some screen shots (with project and encoders settings, layout with scopes, player):

Link to archive with source video, project files, resulting videos and attached screen shots (~70MB):

https://www.dropbox.com/s/ueul6jrpdpc2csq/Vegas%2015%20Video%20Levels.zip?dl=0

Thanks.