stop() appears to be a custom command on the Springs Windows driver you are using. It isn't listed as part of the windowShade capability. I'm willing to update the shade section of the app but only to be compliant with the capability. As you can see below, there are startPositionChange() and stopPositionChange() commands available. I can add these but it won't do anything for you if it's not implemented in the driver. Let me know if the author of the driver is willing to add this to the driver and PM with a link to the driver after it has been updated. I will then update the ABC app to support it but I'll need you to test it out for me before I post it officially. I don't have any shades to test myself.
WindowShade
Device Selector
capability.windowShade
Driver Definition
capability "WindowShade"
Attributes
position - NUMBER, unit:%
windowShade - ENUM ["opening", "partially open", "closed", "open", "closing", "unknown"]
Commands
close()
open()
setPosition(position)
position required (NUMBER) - Shade position (0 to 100)
startPositionChange(direction)
direction required (ENUM) - Direction for position change request ["open", "close"]
stopPositionChange()
