This message is part of the retry mechanism of brainCloud. The error code is 40605 = MISSING_LAST_PACKET_RESPONSE .
If the brainCloud client times out without receiving a response from the server, it will automatically retry for you.
During a retry - one of three things will normally happen:
The system may be still processing the request - in which case it will respond with PACKET_IN_PROGRESS (and the client will automatically retry again)
The system may have completed processing the request, and your client somehow missed the response. The good news is for that case we cache the response - and so the server will just return the cached response - like everything is normal.
In the third case, the client for some reason didn't receive the response - but the server was also unable to cache the response, because the response was too large - so you receive the MISSING_LAST_PACKET_RESPONSE error.