The front head bolt holes are blind holes,meaning they have a bottom.A lot of times when I do this job,I have to use a vacula to suck oil out that settles in the holes when the head is removed.If oil has gotten into the holes,the bolts could be hydraulic locked.If this is the case,the head is not properly torqued and could leak or even worse,warp.
Its worth checking.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."