Hi Mahlon,
I've created a ticket for this.
This only seems to be happening for the first Action Result listed in the dropdown, and only on first selection. If you select any other option from the dropdown, it should insert, at which point you should be able to re-select the first one and have it insert successfully. If there's only one Action Result to choose from, you can temporarily create a second one within the action set to perform this workaround.
I'll keep you posted.
- Justin