Is it possible that you'd disabled reset before send in the Web IDE?
If so it'd be trying to upload code, but the previous code would be running in the background so could be using CPU time and causing the upload to fail?
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Is it possible that you'd disabled
reset before send
in the Web IDE?If so it'd be trying to upload code, but the previous code would be running in the background so could be using CPU time and causing the upload to fail?