The Problem described in this Thread is Almost exactly What happened to us and we describe here at Point 3. thought it might be helpful to Connect those Infos / Threads for further Investigation .
Our Source Material is/was everytime in the original cubase „Audio“ folder and was Never Moved before, after or while using the „Export to vst live“ Feature from within cubase.
We have the feeling that there might be an issue with „linear vs nonlinear“ source footage?
At least re-Rendering all Audio Material to Full Length Source Audio Files is What Instantly made the Audio Files Stick on our vst live project and Werent lost / empty for Almost a week and Dozens of project Save Intervalls now 