I am trying to apply the mirror modifier on my model, however when I do it shows a split, despite having the clipping toggled on. I changed my pivot point to 3d cursor and pressed these keys S + X + O to automatically align the unclipped vertices however this doesn't work. I believe it's due to the vertices not properly aligning to the axis, however I'm not sure how to do this. Below are images of the vertices without mirror modifier and with mirror modifier.