Hi
Found a bug when using the Vegas Defocus FX tool (in Vegas Pro 15 build 216), see attached images, the arrow indicates the glitch when Intel acceleration is on, the other image is with it off.
To replicate:
Drag a video clip to the time line, mine is an H264 encoded clip.
Add the Defocus FX effect, select the preset "Circle, Moderate bloom", then back down the Radius to around 1.08 to see it more clearly. When GPU acceleration is set to the Intel GPU Graphics (I'm using a i7 7700) there is a strange effect at the edge of the bottom frame. This appears in the final render, but doesn't appear if you use the screen shot tool to export a frame as an image.
Change under preferences to not use acceleration, save the project then restart Vegas for the setting to take effect, reopen the project. Notice the artefact has now gone.
Regards
Phil