Why do text render files keep disappearing!

[bryboru64]

I am editing a 90 minute film with multiple text IDs adnd a credit role.  Sometimes those render files will magically disappear, becoming unrendered and I have to re-render, which can take up to 40 minutes.  What gives!?

[Ann Bens]

I have seen previews disappear.

Sometimes dropping an adjustment layer over the footage, then turning it off (poking the eye) will magically make the render appear in the timeline.