[Mauro Moreira] “The only thing that remains is that sometimes when I export Mov or MXF from a h264 source, the render comes out with a lot of Media Offline. Nothing that i tried solved this (slowing down render, etc).”
Is this on Resolve Studio?
What OS are you using? What hardware (CPU, GPU, RAM, I/O)? What type of camera source files?
Make sure you check Prefs -> User -> Media Storage to see that all of the source drives are shown in the display. The top-most drive is the location used for Gallery Stills and Cache Files, and the other drives are for source files. As a safety, you could check the Media Page and make sure all the files have valid source directory paths. Relink them if necessary. Also in Project Settings -> Master Settings -> Working Folders, make sure those drive paths are valid as well. As a final step, you might try deleting your current Optimized Media and Render Cache and regenerate them as needed. I have seen Resolve appear to choke when what was actually happening was that some of the Cache files were bad.