DP bats, gets on base, FLEX runs for her. Next half-inning, DP reenters, gets on base again.
Other team now claims the FLEX can't play defense after running for the DP, insisting that's an unreported sub or illegal reentry.
After my trying to get the coach to understand a few times, I'm about to say "I know this is correct, so please let's play", when he says
please ask your partner.
If I came to you as partner, would you know the rule or would you be confused?