Warped rear drum

This is exactly what happens.

 

so if it happens again, get new drums and new shoes installed.

the problem is really going to be in the formulation of the shoes, but because the old shoes 'seasoned' the old drum, it needs to go through a process of 're-seasoning', not all that different from cast iron pans. in a lot of ways, it's quicker/easier to just replace the drums at that point for faster results.