I’ve been reading John Sandford novels since he started writing them. Every Lucas Davenport, Virgil Flowers, Kidd book he’s written. And the handful of other characters and co-authored novels. In all of these books I don’t recall finding a continuity error. Every plot seamless. But I came across the following while re-reading Dark of the Moon (Virgil Flowers)

“Knock at the door. Bad news. Bad news always knocks quietly. He thought of his son in Minneapolis, this daughters in Alberta Lea and Santa Fe.’
— Page 111, Dark of the Moon

And just six pages later…

“This is brutal, Virgil said, standing with his hands in his jeans pockets. “The family hear yet?”
“Not much family, not that we k now of — maybe she has cousins. They never had children.”
— Page 117, Dark of the Moon

I checked and double checked and the reference is to the same minor character. I guess this could be explained by the speaker (a deputy) in the first quote not knowing the dead couple (locals) had children, but that’s a stretch.