Riser cables - rubber

Hi all,

Ive just ordered new risers and testing them out before putting them into my new rigs.
Today I woke up looking at my test rig to find out most of the rubbers were hanging and about to fall off.

Room temperature 20c / cards at 65/70c

I already pushed them back onto it at this point.

http://imgur.com/a/DGAaL

Is this normal or did the my chinese seller used a cheaper glue or something like that?

Any advice appreciated,

Thanks

Sjeikz