It's crossed paths with sales addresses over multiple addresses with amounts that are too large for individual sales transfers and too consistent/regular to be for paying electric expenses.  The multisig address (3Mkw) has inputs from 1KYXrw4Ftkmomfs4iyVXUSqQeRX75Unoi8, and repeatedly puts outputs through to 19iVyH1qUxgywY8LJSbpV4VavjZmyuEyxV, which I identified as a nexus in my OP.