I have had two different 24" sequential DRL (white) / sequential turn (yellow) strips on my Slingshot.
The first set worked flawlessly. They were "side firing" so, I had them mounted underneath the front valance. Emergency flashers worked perfectly with key on or off.
Unfortunately, since they were mounted on the under side of the valance, they got torn apart when exiting a parking lot.
I replaced them with a set that would mount on the front of the lower valance. These work fine when the Slingshot is running. DRL, turn signal, emergency flash.
Turn the key off and no more emergence flash. A brief flash can be seen....that's it.
I am assuming that there is no consistency on how these "cheapy" LED strips are manufactured / controlled.
The current set appear to require the constant 12V from the running light as the "power source" and the blinker is a trigger to begin the sequential amber. Without that 12V, flashing just won't happen.