What device handler are you using for the Hue dimmer?
I ask because technically the hue dimmer switch is a ZLL device, not a ZHA device, So smartthings doesn’t guarantee it will work, and we might have to let them off the hook for that one. Neither Phillips nor smartthings say it will work with the SmartThings hub. There are some experimental device type handlerS that people have been trying with it, but it’s not the same thing as if, say, a ZHA pocket socket stopped working.
I do use the dimmer switches at my house, but I use them as a parallel means of control, I don’t try to get SmartThings to recognize them.
It doesn’t change the basic issue of instability , and trust me, I know that as well as anyone, but sometimes SmartThings is not at fault.