OK here we are a year on from your post.
I am running FCPx last year’s version.
FCPx has been eating up disk space since i got FCPx last month. I have moved stuff to drives to free up space, but its getting tight in here!!
this morning I booted up FCPx and I had 2.5 Gb left – from 40GB last week!
Anyway, today all i did was cut and delete 3 small parts from a timeline clip. About ten mins work after boot up. I ran out of HD space. Like 2.5GB gone in ten mins with 3 cuts..
It can’t be rendering from last time used surely?
So I found this post and realised it was an issue.
I have done as you say but there is no Render file inside my app – package contents – it just doesn’t exist..
The only render folder is in the project folder.
Have you come across another way?
Thanks
Sacha