Hi, I have added my Philips Hue system to SmartThings. Every couple of days the devices from the Philips Hue repopulate into a room in the SmartThings app. The original population stays intact and I am able to delete the extras without issue.
How do I stop the Hue devices from adding duplicates into SmartThings?
Connecting Hue is one of the trickier integrations with ST because there are several methods available. It sounds like you may have used two different methods which is causing the duplicates. That is one possibility. Can you provide a few more details: 1) this is the first time you added Hue to ST? 2) can you go through the set up process you took to add them (go through the process in the app and carefully look as there are a couple of links on each screen)… one near the top (linking your account - which is the cloud to cloud connection) and at the bottom of the Screen (next) which is the direct LAN connection and there is also the Matter integration but not on that screen. Which option did you choose? Don’t complete the add again when you are looking at those screens. Which hub do you have or appliance if that is the case?
Another possibility is my recollection may be off (@jdroberts has pointed that out) because I already have Hue installed and don’t see the step he points out 
Well, thanks for the fast replies.
I have been running an ST Hub and a Hue Hub that have been linked for about 5 years.
How were they connected? Through the ST Hub, I went to add device and selected Philips Hue. Followed the steps to logon to my Hue account and that was all.
From time to time I have added more Hue Lights, and because the account is linked, they appeared in ST. Lately duplicates of Hue devices continue to appear.
I understand that there are a couple of ways to connect the Hue devices, but that is the only process I have used to date.
When I check by going to add a device and select Philips Hue, I get the message that the partner service is already connected because the accounts are linked. So all should be good.
I know that I can connect Hue devices directly to the ST Hub but have never done that. All my Hue devices appear in my Hue app.
So, I guess I should unlink my Hue account from ST, then see if there are any Hue devices still connected and responding. Then delete all Hue devices from ST. Then re-link the accounts? Thoughts?
Probably remove the linked service under Menu > settings > linked services. Be sure that is what you installed otherwise you may need to fix any broken routines that would result.
After removing the linked, check if the other set of lights still function.
All my routines for Hue are all in the Hue app, not ST.