ethers.js: Unhandled promise rejections en masse

We’re seeing a ton of unhandled promise rejections using ethers 5.0.12:

Error: timeout (requestBody="{\"method\":\"eth_blockNumber\",\"params\":[],\"id\":52,\"jsonrpc\":\"2.0\"}", requestMethod="POST", timeout=120000, url="...snip...", code=TIMEOUT, version=web/5.0.11)
    at Logger.makeError (/opt/indexer/node_modules/@ethersproject/logger/lib/index.js:179:21)
    at Timeout._onTimeout (/opt/indexer/node_modules/@ethersproject/web/lib/index.js:148:35)
    at listOnTimeout (internal/timers.js:549:17)
    at processTimers (internal/timers.js:492:7)

The setup is as follows. After creating the Ethereum provider, we use it to make a number of contract calls and create transactions (as you would).

    const ethereum = new providers.StaticJsonRpcProvider(
      {
        url: ...,
        user: ...,
        password: ...,
        allowInsecureAuthentication: true,
      },
      "mainnet"
    )
    ethereum.pollingInterval = 4000

    ethereum.on('debug', info => { ... })

    ethereum.on('network', (newNetwork, oldNetwork) => {
      logger.trace('Ethereum network change', {
        oldNetwork: oldNetwork,
        newNetwork: newNetwork,
      })
    })

    logger.info(`Connected to Ethereum`, {
      pollingInterval: ethereum.pollingInterval,
      network: await ethereum.detectNetwork(),
    })

We have tested custom Ethereum nodes, Alchemy, Infura — the behavior is the same across all of them. I’m not entirely sure what leads to the eth_blockNumber calls, why they happen so frequently and why they all time out.

I’d be happy to provide more details if needed though.