Black screen in iPhone photo edit when I zoom out

I’ve been using edit in photos to draw over photos on my iPhone 12 Pro Max. I bought it pre-owned from Plug.com.

As im almost finished editing, when im zoomed in doing details then zoom out, the screen where the pic should be turns black. I can still see the top where it says CANCEL ↩️ ↪️ Markup DONE.

I tried clicking DONE & UNDO but it never saves where I left off. iPhone has up to date software. Any thoughts? Thanks. it only shows the processing icon bc I clicked DONE after it went black