If anyone else gets the same git corrupt / 'empty object' errors I've been getting I think I've found a fix (but there's still a chance you might lose any work that hasn't already been committed and pushed to codebase).
Take a full backup of your zatpark folder via terminal (probably need to do this on root user):
cp -a /home/zatpark /home/zatpark-old
Find & delete all the corrupt/empty objects in git:
find .git/objects/ -type f -empty | xargs rm
fetch the missing objects and run a check:
git fetch -p
git fsck --full