Hi James, @jameslthomson,
Sorry for the delayed response – I didn’t have internet access for a couple days.
Don’t worry – a 1 cm misalignment at the ends of a seam isn’t a big deal, and it’s not worth trying to re-seal the seam. At worst, you might have a small wrinkle near that corner.
You can either leave it the way it is or trim the protruding piece flush with the shorter one. Depending on which pieces they are, you may find that that corner doesn’t end up exactly where it should on the floor, but that’s okay – just position it as close as possible.
Does that make sense?