A catastrophic memory leak occurs when you use the "Sapphire render" plugin. This happens when using any video formats and any encoders. 64 GB RAM is enough for 5 minutes of rendering 1080p video. Then there is the collapse of "VP15". When you enable "GPU acceleration via GTX 1080", collapse occurs even faster, as soon as the 8GB memory card. Moreover, the used memory is not returned after a successful rendering process. It's awful! I can't complete any project!
A similar problem was described here https://www.vegascreativesoftware.info/us/forum/xavc-l-loading-problem-v14--103623/ but not solved. As it turned out, the problem is much more serious and not related to a specific video format or encoder.