Be warned that "Real/Genuine" Gaffer Tape sticks so well that it can really damage what it is stuck to if it is removed.
Incorrect, real duct tape, is designed to be removed without damage. You would be confusing this with gorilla tape.
As regards the original question, I've brought loads of gaffer tape, of ebay and never had any issues. Also use Amazon, where it's possible, to check reviews for the product itself.
If it doesn't move and it's meant to =WD40
Does it get teenagers out of bed.![]()