Node server is getting down with error buffer.js:488 throw new Error('toString failed');

We have an app build on nodejs (Server A), which is fetching data from another nodejs app(Server B) using REST API's.

Similarly for downloading files Server A make request on Server B and Server B fetches files from AWS S3 and pipes the data back to server A.

This system works perfectly and we are able to download files upto 1GB.

Issue is sometimes Server A crashes with below error:

    buffer.js:488
    throw new Error('toString failed');
    ^

Error: toString failed
    at Buffer.toString (buffer.js:488:11)
    at Request.<anonymous> (/var/www/sky/portal/node_modules/request/request.js:1145:39)
    at emitOne (events.js:95:20)
    at Request.emit (events.js:182:7)
    at IncomingMessage.<anonymous> (/var/www/sky/portal/node_modules/request/request.js:1091:12)
    at IncomingMessage.g (events.js:273:16)
    at emitNone (events.js:85:20)
    at IncomingMessage.emit (events.js:179:7)
    at endReadableNT (_stream_readable.js:913:12)
    at _combinedTickCallback (internal/process/next_tick.js:74:11)
    at process._tickCallback (internal/process/next_tick.js:98:9)

We are not sure from where app is getting crashed. Please suggest.

via A_J