DETROIT — A preliminary exam for the parents of a teenager charged in the Nov. 30 Oxford High School shooting could be delayed next week due to legal issues being raised by attorneys over evidence, witnesses and “love you” objections. Ethan Crumbley, 15, is charged with fatally shooting four fellow students and wounding seven other victims, including a teacher. His parents, James and Jennifer Crumbley, have both been charged with four counts of involuntary manslaughter for buying him a handgun as a Christmas gift and later allegedly failing to properly secure the weapon or advising school offi…