Things3 Apple Script sandbox error

I'm using a very simple macOS script to add todo's from my Things3 in Fantastical. The reason I'm doing this is that I want more control over what is being added to the calendar event. You can add todo's from Things3 to fantastical using drag and drop, but this will add a lot of data to the event title that I want to filter out. The script I'm using is:

tell application id "com.culturedcode.ThingsMac"
	set title to name of selected to dos
	set description to notes of selected to dos
	set eventLength to " 30 minutes"
	set calender to " / Calendar"
	set input to (title & eventLength & calender) as string
end tell

tell application "Fantastical"
	parse sentence input notes description
end tell

This worked fine in the past, but with new sandbox settings(?) it looks like it's being blocked. When executing the script from Things3, I get:

Sandbox: Things3(989) deny(1) appleevent-send com.flexibits.fantastical2.mac

Is there a way to get around this? The strangest thing is that when I run the script outside Things3 it works fine. But when it is invoked from Things3 (described here ) it gets caught in the sandbox.