ion: Wallet file verification failure on npm run bitcoin

I’m following installation instruction to get a working testnet ION node. I have a single instance of bitcoind, mongodb and ipfs running and then I get this:

$ npm run build && npm run bitcoin

...

Collection 'transactions' found.
Sending jRPC request: id: 5mq6r6sfrah, method: createwallet
Wallet with name sidetreeDefaultWallet already exists.
Sending jRPC request: id: 3624m93nnhi, method: loadwallet
Sidetree-Bitcoin node initialization failed with error: {"stack":"Error: Unexpected fetch HTTP response: [500]: {\"result\":null,\"error\":{\"code\":-4,\"message\":\"Wallet file verification failed. SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of Bitcoin Core?\\n\"},\"id\":\"3624m93nnhi\"}\n\n    at BitcoinClient.<anonymous> (/home/dr/ion/node_modules/@decentralized-identity/sidetree/dist/lib/bitcoin/BitcoinClient.js:815:27)\n    at Generator.next (<anonymous>)\n    at fulfilled (/home/dr/ion/node_modules/@decentralized-identity/sidetree/dist/lib/bitcoin/BitcoinClient.js:5:58)\n    at process._tickCallback (internal/process/next_tick.js:68:7)","message":"Unexpected fetch HTTP response: [500]: {\"result\":null,\"error\":{\"code\":-4,\"message\":\"Wallet file verification failed. SQLiteDatabase: Unable to obtain an exclusive lock on the database, is it being used by another instance of Bitcoin Core?\\n\"},\"id\":\"3624m93nnhi\"}\n","code":"bitcoin_client_fetch_unexpected_error"}