The SOAP response indicates that an error occurred on the server

Today, I faced a strange problem with an error: “SOAP response indicates that an error” working with SharePoint Online and InfoPath form customization. The task seems to be very simple, I had to customize the custom list form. And I am still a big fan of InfoPath, so just a few clicks and the form has been customized, then press Quick Deploy and … Ups… Something new comes to me.

The SOAP response indicates that an error occurred on the server:

The server was unable to process the request. —> Server encountered an internal error. For more information, turn off customErrors in the server’s .config file. —> Server encountered an internal error. For more information, turn off customErrors in the server’s .config file.

What’s the hell??? It was strange to me as just a few days ago, it was working without any problem on this site collection. Finally, I found a solution, which is still strange to me…

This site collection has an event receiver fired when the list event “ItemAdding” occurs, and it’s limited to work just with my custom list. And it seems that for the event receiver, the list form customization will also fire the event! So, in my case, I had to turn off event receiver future, then deploy a customized form and turn on event receiver future. It works now.