Suddenly, sketch data upload(SPIFFS) fails over serial although the sketch itself can be uploaded normally. No settings in the Arduino IDE Tools have been changed and the serial port is the same. Here is the output from the attempt(not much help): esptool: error: unrecognized arguments: --end SPIFFS Upload failed!"
The only thing that has changed since I last uploaded SPIFFS was my router was reset and it renumbered the IPs of both the NodeMCU and the client PC. Suspiciously, the web page receiving the NodeMCU data now hangs but there nothing in the sketch or the HTML/Javascript that has hardcoded IP addresses.
Why would this impact SPIFF data upload over serial?
There was a recent bug in the SPIFFs plugin related to transitioning from Python 2 to Python 3 that caused this issue.
Update your plugin to the latest version.
https://github.com/esp8266/arduino-esp8266fs-plugin/releases