Worksession renders - output size won't change

I’m using worksession to link 3 files. Worksession is now being used solely to render, i.e. the only object in the worksession file is the sun. The problem that I’m having is that when I try to change the output size it still just renders at 800x600 (which I had used a while ago to do quicker test renders). When I go into the vray options panel the output size says 3000x2500 (which is what I want). I’m not sure why it’s saying one thing but doing another.

Can anyone help? Thanks!

Forgot to mention another worksession-related issue:

If I try to render in the individual files v-ray just loops and all I see is a blank grey vray frame. But the same model will render once I’m in the worksession file.

Here’s a screenshot of what I mean. I have done a number of renders previously with these same files at the desired 3000x2500 size. This problem occurred once before but it seemed to go away. It’s now persisting despite closing and restarting rhino.

Thanks again!