layer is locked when viewing photos in Photo Bin

Hello - i've been using Photoshop Elements for years (doing the same kind of things) and this is the first time I encountered this issue. I usually drag a bunch of jpegs from my folder to PE editor. Today when I did that, when I try to use keypad to move from one picture to next in the Photobin, I see a pop up message "could not nudge the data because the layer is locked." I couldn't find anything online so hoping someone here can help. Thank you!