apollo-server: Runtime.UnhandledPromiseRejection, Error: called start() with surprising state invoking serverWillStart

This is a very strange behavior indeed. We just started seeing this in our GQL stack this morning. I’ve reset out development environment to our stable branch to ensure that this is not related to a recent code change we have made, but the problem persists. I have been unable to find the source of this issue, and has left me quite befuddled.

{
    "errorType": "Runtime.UnhandledPromiseRejection",
    "errorMessage": "Error: called start() with surprising state invoking serverWillStart",
    "reason": {
        "errorType": "Error",
        "errorMessage": "called start() with surprising state invoking serverWillStart",
        "stack": [
            "Error: called start() with surprising state invoking serverWillStart",
            "    at ApolloServer.<anonymous> (/var/task/node_modules/apollo-server-core/dist/ApolloServer.js:230:23)",
            "    at Generator.next (<anonymous>)",
            "    at /var/task/node_modules/apollo-server-core/dist/ApolloServer.js:8:71",
            "    at new Promise (<anonymous>)",
            "    at __awaiter (/var/task/node_modules/apollo-server-core/dist/ApolloServer.js:4:12)",
            "    at ApolloServer._start (/var/task/node_modules/apollo-server-core/dist/ApolloServer.js:226:16)",
            "    at ApolloServer.<anonymous> (/var/task/node_modules/apollo-server-core/dist/ApolloServer.js:280:22)",
            "    at Generator.next (<anonymous>)",
            "    at /var/task/node_modules/apollo-server-core/dist/ApolloServer.js:8:71",
            "    at new Promise (<anonymous>)"
        ]
    },
    "promise": {},
    "stack": [
        "Runtime.UnhandledPromiseRejection: Error: called start() with surprising state invoking serverWillStart",
        "    at process.on (/var/runtime/index.js:37:15)",
        "    at process.emit (events.js:203:15)",
        "    at process.EventEmitter.emit (domain.js:448:20)",
        "    at emitPromiseRejectionWarnings (internal/process/promises.js:140:18)",
        "    at process._tickCallback (internal/process/next_tick.js:69:34)"
    ]
}