Hi Msiebers,
the stuff (the very thick silicon) does not leak as such --- it 'creeps' but only very little.
In fact all silicon does creep, that's why it is 'poison' in anything with open/unprotected contacts.
The bottom of the lift is open, because it would not work when air be trapped in the piston sleeve. It only needs 1/2 of a pin-head to be applied on the piston and it works again for some year(s). Initially often too good rather i.e. going down too slow.
But since Lloydc bought a new lift, problem is fixed --- until this one starts plying up after some time. Everything need to serviced after a while :-)
Greetings,
Axel
PS: I'm not so sure about that damping grease (link). I tried some (another item) and it did not work at all, the lift with arm just dropped.