Complete the defining contact clause and leave the preposition at the end: This is the scheduling problem ___. Use exactly I, told, you, about, and earlier in that order, with no added words.

Erklärung

I is the clause subject, while the problem is understood after about, so the object relative element can be omitted. Retaining it after about would be the closest error because it would resume an antecedent already represented in the clause structure.