I'm seeing "A Component Error has Occured!" message when I'm trying to edit a page in the Lightning App Builder.

"message: Uncaught Error in $A.getCallback() [Unexpected end of JSON input]
Callback failed: apex://box.UIElementController/ACTION$downscopeToken"

Component Descriptor
markup://box:UIElementUpload

Filename
https://d4r000001w40muas.lightning.force.com/flexipageEditor/components/box/UIElementUpload.js

Function
Object.eval

Line 41 Column 37

Stack Trace
Object.eval()@https://d4r000001w40muas.lightning.force.com/flexipageEditor/components/box/UIElementUpload.js:41:37