Cannot Edit any Blocks on Product Pages: Open & Disappear in 2 sec

I am trying to edit blocks on my product pages. When I click the edit button, the box for the block briefly opens but then force closes. FYI this happens for any block on the page. 

This is really frustrating and comes along with a string of other issues for Squarespace over the past month. I need to edit my product pages asap. 

Update: It does work in the "New Editor" - I liked using the old product page editor,, so forcing me to change via this method is frustrating.