Re: Pesky header
jigsprocket .... I'm not 100 % clear of your layout but from what I have in my mind .... is there a main beam that runs underr the floor?
If so this maybe a hump from the main beam being higher .... which might be from the exterior ends of the foundation settling..... or the center has heaved.
Whether or not the cracking of the ceiling is related to this depends on how this upper beam as you call it is supported on the ends and what method of framing is above this.
"" an ounce of perception -- a pound of obscure "