niabi Indeed your SYSTEM image is too big. You might want to change compression method to gzip or xz, whichever fits 512MB.
Edit: I noticed that you changed the size some days ago. This is generally not a good idea, users cannot upgrade after size change. Using a different compression may help you keep the size below 512MB.
I was able to compile myself changing back to 512MB partition. I just removed one of the ES themes to get under 512MB without changing the compression.