Are you using them connected to a Hue hub or are you trying to connect them directly to a SmartThings/Aeotec hub?
While it is technically possible to use them without a hue hub, neither company recommends it or will provide support if you choose that option. For one thing, this can lead to lost Zigbee messages on your network.
See the following:
FAQ: Do I need the Hue Bridge/Hub to Use a Hue Bulb with SmartThings?
The other thing is that if you are using them without the Hue hub, a number of community members have reported Zigbee issues since the most hub recent firmware update and they would be subject to the same issues.
Devices randomly switch On / Off after 0.45.9 Hub upgrade
If you are using them with a hue hub, I’m not sure what to say: most people find them very reliable in that configuration. The most common explanation would be local Wi-Fi interference. So you might need to change channels. 