Nope. I have my LIFX bulbs connected to the main LIFX app, HomeKit, Home Assistant and Homebridge and I’ve never once seen a duplicate.
Edited to add: except when I did it on purpose, i.e. when I forgot to filter out specific bulbs from Homebridge or Home Assistant and thus got duplicates in HomeKit.
So, the Alexa skill isn’t what is telling SmartThings the new state of your lights. Removing that (and forgetting the duplicate devices in Alexa) is for removing duplicates in Alexa. Unfortunately it’s not obvious which devices come from the LIFX skill and which ones are from the SmartThings skill. So it might be easier to forget all devices and redo discovery.
As for updating. To clarify, if you have the smartThings app open on a light, does the following happen?
Use smart things app to turn light off. The smart Things app should now say the light is off
Use Alexa or the App to turn on the light
SmartThings should, within 90 seconds, say that the light is turned on without you having to do anything in the smart things app.
If smart things doesn’t change, then it’s possible that there was a problem when you linked the LIFX skill in the SmartThings app and so our cloud doesn’t know how to send updates to the SmartThings cloud when your lights are changed.
In this case, are you able to choose the “Contact Support” option in the settings section of the LIFX app. Mention this thread, your samsung account email, and your LIFX account email. And I’ll see if I can follow up on this.
I thought you were talking about the LIFX tile, I’ve never heard of ActionTiles before. A quick google brings up https://www.actiontiles.com/. I’m unfamiliar with how they keep updated. I would suggest asking them.
As for the SmartThings app, I’m not sure why it would update at all if it’s taking longer than 90 seconds. I would say it’s still worth making a support ticket with us about it.
Does the Smartthings Alexa integration allow you to choose which devices are synced? I’m a Google Assistant user and I just make sure Smartthings doesn’t tell it about anything that can link directly. There are settings in the SmartApp.