So they were caching range proofs and it's a caching bug? Like in that they bypass verification of the rangeproof on a cache hit? That's what I'm seeing now. If so, that's... terrible?
This patch seems to be the fix: 
GitHub
fix: range proof cache bind to asset and scriptpubkey · ElementsProject/elements@c26d719
Open-source implementation of advanced blockchain features extending the Bitcoin protocol - fix: range proof cache bind to asset and scriptpubkey ...