If I go for LASIK enhancement 1 year later, will the corneal flap adherence weaken as it has to be opened again?

With LASIK enhancement, the flap is opened and the underlying stromal bed is treated again to remove residual spectacle power.

The effect on flap adherence is the same as after LASIK for the first time, ie that initially it will be weak and then eventually as the cornea heals, the adherence will go back to the way it was before the LASIK enhancement was performed.