javascript - NestJS och Express orsakar intermittent UnhandledPromiseRejectionWarning

Jag kan för allt i världen inte lista ut detta. Det händer då och då och orsakar inga problem med själva applikationen, men jag har ingen aning om vad som orsakar det. Jag gör samtidiga anrop till API:et från webbläsaren om det har något att göra med det.

[Nest] 16608   - 11/7/2018, 1:23:08 PM   [NestApplication] Nest application successfully started
[Nest] 16608   - 11/7/2018, 1:23:23 PM   [LoggerMiddleware] Request /api/observation-statement/pending-count +14943ms
[Nest] 16608   - 11/7/2018, 1:23:23 PM   [LoggerMiddleware] Request /api/observation-statement/revision-count +16ms


(node:14968) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
at ServerResponse.setHeader (_http_outgoing.js:469:11)
at ServerResponse.header (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\express\lib\response.js:767:10)
at ServerResponse.send (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\express\lib\response.js:170:12)
at ServerResponse.json (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\express\lib\response.js:267:15)
at ExpressAdapter.reply (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\@nestjs\core\adapters\express-adapter.js:44:52)
at ExceptionsHandler.catch (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\@nestjs\core\exceptions\base-exception-filter.js:16:33)
at ExceptionsHandler.next (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\@nestjs\core\exceptions\exceptions-handler.js:15:20)
at C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\@nestjs\core\router\router-proxy.js:23:35
at Layer.handle_error (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\express\lib\router\layer.js:71:5)
at trim_prefix (C:\Users\Ricardo Saracino\IdeaProjects\sor-api\node_modules\express\lib\router\index.js:315:13)
(node:14968) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:14968) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Jag har reducerat anropen till en ganska enkel funktion, och ser till att anropet returnerar ett unikt värde (jag trodde att det kunde vara ett 304-problem)

@Get('revision-count')
async countRevisions(@User() user, @Param() params) {

    user.count ++;

    return {
        status: 'success',
        data: {
            rand: user.count,
        }
    };
}

detta hände innan mellanprogramvaran