MySQL default values and double save()

Hi everyone! And sorry for my english.

I have table with some integer fields NULL DEFAULT '0' and I have this php code on phalcon v2.0.3:

$robot = new Robots();
$robot->email = $this->request->getPost('email', 'email');
$robot->ip = $this->request->getClientAddress(true);
...
//I skip fields with default values
...

if ($robot->save()) { //after this save() skipped fields have value 0, all right 
    if ($this->request->hasFiles(true)) {
        foreach ($this->request->getUploadedFiles(true) as $file) {
            ...
        }

        if ($robot->image_id == 0) {
            $robot->image_id = $images->id;
            $robot->save(); //but after this save() skipped fields have value NULL, why?
        }
    }
}

I tried

$this->useDynamicUpdate(true);

but it's not help me, I tried annotations, but it's not help me.

If i use

$robot2 = Robots::findFirst($robot->id);
$robot2->image_id = $images->id;
$robot2->save()

instead of second

$robot->save();

all right.