I got a T5 stick has been used since the launch. I did not abuse it, but the buttons feel pretty sticky now.
I used to use WD40 on my HORI FS EX with similar problem, but WD40 got a terrible smell and I think it is quite toxic.
There seems to be some silicone based lubricant, such as Jig-a-Loo, however, after some research, that one seems to be toxic too. Any non-toxic one people could recommend?