In SciFi stories, there may be many key elements to your plot. And then there may be smaller minor details. It may be very easy to forget these small details when writing, and that leads to an inconsistent plot.

Say your character has robotic legs and you make her bleed from her legs- that doesn't make sense because her legs are made of metal!

Another thing that needs to be consistent is technology/ the world which your book is set it. You can't have a world which is a barren wasteland with no technology and then suddenly a hover board appears.

A way to make sure you don't forget small but important details about your plot is to make a big mind map of all the things in your story that stay the same throughout. You can always look back to it when writing so you don't forget anything.

A consistent plot means the reader is neither confused or put off by the obvious mistakes!