The problem was the reorganize command in itself. Reorganize is used by the client to switch to a stronger chain. The problem was that there was an old bug which did not forget contracts (beacons, polls, votes etc) when detaching blocks from the weaker chain. Previously this just left the node in a goofy state but with the stronger beacon checks in V9 this caused nodes to start forking instead.

We have tested @tomasbrod's reorganize rewrite last night and so far it's looking good.