I've been inserting small bits of data from Filemaker Pro into other systems we've written for some time using "OpenURL".  However, this approach works, but leaves you with a browser window open, and isn't able to see what the other system returns.  So moving to the "Insert from URL" script step instead.  This seems to work fine when the "Insert from URL" is the only step in a script, but it doesn't complete satisfactorily when "Insert from URL" is one of multiple script steps.  What could be happening?  My first thought was that perhaps the script step isn't given enough time to complete, but now I'm not sure that's the answer.

My first, perhaps obvious, question would be: is the Insert step executing while the target field is available? The field needs to be on the layout for any of the Insert steps to work, including Insert from URL.

And you might want to put a 0.5 second pause in afterwards, if it's a lot of data you're inserting.

If you use the FileMaker Advanced, you can use the Debugger; it will give you an error number when something goes awry. Then you can look up the error by the number and see what you need to modify.