A few commands I use to help me figure out what is filling up space:
Find files in a FS larger than 50 MB
find / -mount -size +50M -exec du -h {} \;
You can change the mount point to the filesystem to whichever you’re searching. You can also change the size, just make sure you have the “+” before it otherwise it will search for the exact size.
Find deleted files but a process is keeping the file handle open
lsof -a +L1 /
Again you can change the file system to whatever. The names will show “(deleted)” at the end and the output will also show you the process keeping them open. When the process get’s stopped it releases the file handle and the disk space is freed.