I transfered my blog to a new domain. And noticed the post function was very slow it loaded 500kb everytime. I noticed the problem has something to do with the import attachment function to the database. It does something and corrupts it somehow.
When I only import the posts with wordpress and upload the attachments and fix the paths manually in phpadmin there is no bug. And it loads 24kb everytime I open post now.
This bug I noticed hammered the traffic usage on my host aswell.