Our flange was broken in three places after 1 year of intermittent use. I've posed the same question about flange removal and replacement to the service department. Will update this thread when Jason replies.
Update: Had the flange replaced by RV Service Center. Flange was glued to short pipe (see below) which was inserted through a rubber "grommet" into the top of the black tank. After considerable effort, I gave up for fear of breaking something during removal. RV service tech said that he also struggled mightily to get it out (he had to confer with Jason. Thanks Jason). Tech replaced flange with similar part and had to chamfer (grind to form a bevel) and lubricate to get the "tail pipe" reinserted through the rubber grommet. Perhaps Oliver construction team should lube pipe well before installing. Should have been an easy fix, but wasn't.
