I'm aware that you're talking about a BP- but most rat snakes don't do second clutches either. I don't breed BPs, but I don't know why that would preclude the possibility? Anyway, I offered my opinion because what you're describing is exactly what I see with my rat snakes. And btw, my 2 FL rat snakes have never bred at all- so in theory, they shouldn't be laying ANY clutches-but they've been doing so yearly since they became adults. And I've bred plenty of snakes in the past (just not BPs) & they don't always "follow the manuals", lol. Good luck.
I hope your snake isn't egg-bound, & it sure couldn't hurt to offer a nest box, that was my thought- just on the chance.