assertion failure, bind() issue

I'm continuing to have issues that I believe are related to using bind(). The call of the function returned crashes. I don't know how to repro it in a simple situation yet. I do have a stack back-trace. The assertion is in jsvRef:

ASSERT(var && jsvHasRef(var)) FAILED AT src/jsvar.c:622

The lower part of the stack is (top-down):

jspePostfixExpression at /big/home/src/esp8266/Espruino/src/jspar­se.c:1424
jspeFactorFunctionCall at /big/home/src/esp8266/Espruino/src/jspar­se.c:1157
jspeFunctionCall at /big/home/src/esp8266/Espruino/src/jspar­se.c:618
jsvCopy at /big/home/src/esp8266/Espruino/src/jsvar­.c:2051
jsvRef at /big/home/src/esp8266/Espruino/src/jsvar­.c:622

Any clue? How can I troubleshoot this? Any way I can find out which JS statement caused this?