I'm not able to perform the bulk update using either an embedded system (ESP8266) or sending a POST request via web based service (https://reqbin.com).
I always get a 400 response with "The request cannot be fulfilled due to bad syntax."
No problem using the standard write data interface (but of course it's limited to one message).
The POST request content is (I have my key instead of XX):
I did a lot of trials changing the number of parameters and the time format, but always with the same result.
Is anyone able to perform any kind of bulk update?