@dhellellerstedt
The reason is simple: The images get uploaded, but not to api.m5stack.com but to 120.77.157.90 (Aliyun/Alibaba Cloud). Simply use that IP and you will get your images. Of course that raises the question why there is this missmatch. Maybe the Firmware-Images in M5Burner got mixed up or some other reason...
Regarding the Tokens: They change each time because only the forst 12 chars are relevant.