I've been working on Blurays recently, and found that using MP4's would lead to a lot of compression artifacts, as well as taking up a lot of space. I then switched to MPEG-2, and found those issues largely resolved. But I've run into a new problem. As more media gets added, the program lags more, and eventually just stops working, and crashes/stops rendering the media. Also, the burned discs and created isos have malfunctioning menus, including all black menus as well as highlights that do not show up. The menus still fully function, but it has a ton of visual glitches.