I just inherited my dad’s antique secretary desk and during the move something jammed. I can only open the slope front about one inch before something catches. The desk has wood loper slides for support.
This might help, but it would be tricky…can you stick enough of your cell phone in the opening to take a picture of the inside to see what’s happened? Of course, you run the risk of dropping your cell phone in there and losing it if your’e not careful. If not, you could try repositioning it at various angles to see if whatever fell out of position inside falls back into its proper place. That’s a long shot, but what have you got to lose (as long as you’re careful).