My 2013 also suffered the dreaded door panel arm rest crack. After sticker shock of replacement panel decided to try and repair the crack before buying a new panel. I saw a youtube video where someone repaired a broken tab on a front bumper cover (). Pulled the top cover of the arm up and used couple of spring clamps to hold it back so could of sort of access the cavity of the arm rest. Used the process outlined in the video and it actually seemed to work, but the arm rest still had a lot of flex and I figured it would crack again. So then I used some JB weld PlasticWeld Epoxy putty (https://www.jbweld.com/product/plasticweld-epoxy-putty). Pretty much filled the cavity in the arm rest, now the arm rest is more sturdy than it was before the crack, and more sturdy than the passenger side door which is not cracked. It has been over a year and it is still doing good, overall cost was less than $20 for super glue and the JB weld which is a lot better than having to drop $400+ for a new panel.