1. Rendering is sequence dependent. You can render one sequence, but when nesting the renders do not carry over to the next sequence.
2. Maybe your disk configuration changed? Using externals?
Why use rendering? What is the purpose?
I render files because I work in m2ts HD files and once rendered I can preview much easier but I have the same problem I can spend 3 hour rendering save my project and when I open it about 3/4 of it needs rendered again
Check in your project settings where the preview files are stored( <Project>-<Project setting>-<Scratch discs>. While (or after) rendering check if the file appear in the location. Save and close project and see if the files are still there.
Is this a special location? Like "Temp" in windows defaults? You might have Windows settings are utility program running to automatically remove temp-file storage location(s).
So change the project settings to <Same as Project>.
Thanks for your reply
I save all my project files to the same drive and the rendered ones are there G:\Adobe Projects\Adobe Premiere Elements Preview Files\ it has all the files
Is G: a networkdrive? Or are your sources on a network drive?
I noticed before that sources on a network drive got re-indexed everytime you start the project. Never noticed that also preview were lost for those, but it could be worth checking.
Great at least I know what is happening I tried three clips I added an air brush effect to one and stabiliser effect to another then rendered the clips (all Green lines) saved the project then opened it and found the red line over the stabilised effect clip it may just be this effect or it may depend on the effect. This started when I added certain clips and adobe asked if I wanted to fix quality problems and I said yes it automatically added the stabiliser effect So far its the stabiliser effect that causes the problem