I had a serial input that regularly failed to send the complete JSON message - an Arduino which was my early experiment with Node-RED. In fact, it was using the CISECO SRF (Slice of Pi) wireless adapters - pre cheap WiFi
I was able to trap the malformed JSON and simply drop the input (since I knew that the platform would send another message 60s later). But the serial in node didn't care at all and kept on working for several years.
This is the setting I used: