Hey,

I am really sorry for the delay of this reply as it is actually a public day off for us here. This is most likely because your hosting company has some security module in place that is preventing such request (with certain contents) to be sent to the server.

They are false positive errors and you can get in touch with your hosting company to look into this. Normally they just need to add some whitelist or disable certain criterias for the POST request but they can definitely see this blocked in their log files.