I've checked it with Bricks support. This was there answer:
"First of all, I am not very sure why the Meta Box team suggested you to reach us. This doesn't makes sense as the Submission Form element was created by them, totally zero code maintained by Bricks. We got no idea how their form works.
I just checked and compared your form setting in the page, seems like you just need to indicate the object type and it's working fine."
So I checked the object type to 'post' and it is working fine now.