Noise wars: does the tenant A not belong in a MF or is tenant B really loud?

[Colleen F.]

What would you do?   Tenant A  is  coming from a SF home rental loved the 1st floor apartment but keeps complaining tenant B on the second floor is walking in the morning too loudly and shutting the door loud.  Tenant B , is an adult working 10 hr a day who gets up for work in the morning at about 6 am and walks in the apartment to get ready for work.  I have told them we can support less noise in whatever way we can (door closer etc) but they need to figure out between them the noise issue. In general this is the only noise complaint I am getting after doing some door planing. Thoughts?  Just let them fight it out?