You will need to provide a much more detailed description of the 'flickering'. For example, is the flickering coming from fluro/neon/LED lights in your video footage? In any event, there are many reasons that can cause flickering that includes a problem with your iGPU or GPU. In order for anybody on the forum to provide an informed opinion about what may be causing the problem, you will need to provide a lot of detailed information about your Vegas Pro version and build, your media (including a detailed MediaInfo report) and your ccmputer. Please refer to https://www.vegascreativesoftware.info/us/forum/important-information-required-to-help-you--110457/ paying particular attention to the information requested under points B & C.