Format View and Format Column Panels are Blank

One of my users has been taking advantage of the column and view formatting features on her list. She used column formatting to shade a date/time column, and she used view formatting to color band every-other row in her list. 

However, when my user returns to either of these formatting panels to make changes, the pop-out panel loads without any content. Below are the results when trying to access the column formatting panel.

We achieve the same result when trying to access the panel to format the view. 

Has anyone else experienced this? I've done a good bit of Google-sleuthing, but I haven't come across anything similar. 

Thanks!