Post becomes unpublished upon editing it and no additional date values or image uploads are possible
I was having a similar problem when editing a node with a field that allowed for unlimited field collection values. Each field collection had 8 input fields, and after adding in over 100 field collection items it stopped adding in more and it would unpublish on Save. 

I could publish it from the content administration screen.

I modified max_input_vars in the server php.ini file from max_input_vars=1000 to max_input_vars=2500 and that allowed for the addition of more field collection items and to keep the node published when saved.