Strange code visible below the footer when Smush is active

I am getting some strange things below the footer on my website. I thought it was maybe related to Hummingbird because I turned on Asset Optimization and moved some stuff to the footer, but I tried uncompressing stuff and moving it back and not getting any changes.

I noticed that the content seems to come from Hustle, so I tried deactivating the other plugins except Hummingbird and Hustle and the issue disappeared. But it came back when re-activating Smush Pro. If Smush is active on the site the issue re-appears.