Sorry, doing this kinda backwards. I started with Future Pinball to experiment. Do you close the VPX editor down and reopen it before a new table is loaded? That is a must in FP thinking memory leaks. Don't see mention of this where you simply close the file only and open another table in the running editor. Testing, it seems to load new tables fine without bombing the app first.
I found different executables in the file structure that launch different versions of VPX. One launches 10.7.4 and the other 'X64' launches 10.8.0. Do you guys use both for older/newer tables? I've used the 10.8 version thinking backwards compatible. Seems to work with no 'old version' prompts with newer games. Why retain two flavors in the files?