I am using VP16 and also have trouble with iphone footage. If I import maybe 20-30 clips it will work but at a certain clip threshold it will not and just crashed in the import process or upon reopening. I always have to convert them and often I even have trouble with the converted files and have to create video proxies just to be able to edit them without lag and thats for only full hd, normally I only do that for 4k. I usually use ANYVIDEOCONVERTER, for some reason sometimes that wont work either and the only way I could create a usable MP4 was to put them in camtasia and render as one big file then chop it up in vegas. Is handbrake better for making these usable?