Unselectable Shape in Acrobat not other PDF Editors

There is a shape appearing on a PDF when opened in Acrobat, but not other PDF editors (I have tried two). I have compromised the document, removed hidden layers, messed with the font, tried selecting and deselecting almost every Acrobat setting. I am unable to select the shape, it does not appear to be "attached" to any other text/shape in the document.

Thoughts?

INB4: I tried on the newest October update and on the previous version.