it also depends on how tightly you clamp up .... ideally as gently as possible without gas bleeding, - it makes the blanket last as long as possible, - but if you get some imperfect mugs, - just crank up the pressure a bit.
You can 'shift' the mug part way through the bake, - my mug press, once it starts the countdown lets me release it, - shift it 1cm and re clamp, - so if you have uneven pressure, - perhaps the blanket is getting a bulge memory, - you get to even out the pressure a bit.
A pita, but a workaround until the box is empty and you buy some good mugs.
As mentioned previous, - Listawood great value, if ebay sells cheaper, they will not be worth the trouble 9 times out of 9.5!