I feel like I've posted this before or on user voice but can't find the thread.
This bug has been around for a couple years now and it's a realy knife to the old workflow. There are two ways to trigger this bug:
Option A (most common)
1. Open PrPro
2. Start a project
3. Add some dynamic linked files (anything, text, vfx, doesn't matter)
4. Leave AE open.
5. In PR. Render timeline green.
6. Close AE
7. PrPro kicks open the BG AE render for dynamic link
8. All render files are now set to red. You just lost whatever renders you've had even though you made 0 changes to the dynamic link file.
1. Open premiere project with dynamic links.
2. Render entire timeline green
3. Open after effects proejct file into the foreground (CMD/CTR+E is usually what does it for me)
4. Change literally nothing.
5. Close AE
6. All Render files go from green to Red, wasting a lot of time here!
Workaround: Don't open or close AE after you've rendered your files. You will still have to re-render though if you ever close and reopen your project.
Workaround 2: Use Render and Replace? Not idea, not as easy as mashing the enter key, slows you down and can cause other issues.