I'm more than willing to cut Larry Niven a break -- when Beowulf Shaeffer got dropped out of hyperspace in "The Borderlands of Sol" until The Ringworld Throne (retitled Ringworld's Children more recently) was more than forty years in author time.
Still, I don't recall any in-universe explanation of how what Bram found to explain ships "disappearing" in hyperspace, especially when too deep in a stellar gravity well,
the presence of hyperspace beasts that literally eat ships when they can catch them, and mostly live near stars
squares with what happened to the Hobo Kelly's hyperdrive in "The Borderlands of Sol", when
the antagonist used a quantum black hole to cause the hyperdrive engine to vanish, dropping Hobo Kelly into normal space ten minutes -- or sixty days under fusion drive -- from normal dropout distance.
Two very reasonable explanations, based on two different understandings of what the hazards are in hyperspace -- but Niven, as far as I'm aware, just left the two seemingly conflicting explanations hanging.
Were these ever reconciled in-universe within the Known Space stories?
"But why can't both be true?" In "Borderlands" and several other stories talking about hyperspace, the danger of running too deep into a gravity well was emphasized; specifically in "Borderlands" Shaeffer says something about the hyperdrive "running off the edge of the universe", trailing atoms of the ship along its path, as if that were a phenomenon that had been detected, perhaps even that there had been hyperwave communication with a ship so afflicted (though I don't recall ever reading anything that specific). This doesn't match up well at all with Bram's discovery.