Yes, its coming from a widget
In old widget it is still uses caller.
This should be replaced by `origin: this.mxform`
To find you widget, open de browser development tools:
Or search in de deployment/web folder of your project.
I found this in the relesae notes of 6.9:
In 6.8.0, we broke the old way of passing the originating page to mx.data.action (using the store.caller property). We fixed the backwards compatibility in this release,. However, we advise you to use mx.ui.action instead, which is simpler yet more advanced. For details on this new and easier way of passing an originating page, see the API documentation. (Tickets 44606, 44773)