Weird problem with scratch disks here. I've set them to a temp folder on the c-drive (not the same folder as my project). Then when I do red line renders, there's no evidence of render files in that temp folder. No folders named for my project, even.
Where are my renders?
When I close and open the project again, the renders are red lines again. They're gone.
I'm running Adobe Premiere CC 2015.3 on windows 10.
Perhaps your boot drive is too full for those files? Anyway, you should not be directing render files to the boot drive, they should be on your fastest drive(s), because they must playback in realtime.
David Roth Weiss
Director/Editor/Colorist & Workflow Consultant
David Weiss Productions
David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.
This is an old, old bug of PPro. When your project file grows heavily up, 50% of your render files are lost. At the beginning of your timeline all is ok. From the middle till the end most of them are gone. They are still there, but the reference is lost. I hope since a couple of years that Adobe will fix it. But I think, the problem is the simple structure of the PPro project file, they must change it.