my bet is that the drums were not turned correctly or the shoes were not ground to fit and haven't yet worn to fit.
I would pull the front drums and examine the drums and shoe contact pattern.
wouldn't hurt to put them on a brake lathe and check them for roundness/concentric with bearing bore.
I don't agree with atomarc that adjustment is the probable cause. While the initial contact could be delayed by a loose adjustment, any pull after that is most likely a contact/fit issue.
