This is so frustrating.
If you got it from a trade, the previous owner must have siliconed it. You can buy some YYJ silicone or put more flowable silicone in there.
Addment: Flowable silicone is supposed to fall out when it’s worn out.
That happened to my eight8eight’s silicone pad.
It looses it’s stickiness, and with a bind, it comes out.
Bottom line: Buy new ones. 
I was afraid someone would say that. -_-
Well you will have to do so. If you want a more durable response, buy some regular rubber O-rings and you won’t have to change your response in a long time.
O-rings rub against the string too much. Does anyone know how to apply flowable silicon correctly? The last time I tried, disaster. 
Just apply it evenly.
Put flowable silicone in the groove, but not outside the groove
Oh, make sure the groove is clean from any ‘stuff’ first.