Not being allowed to modify scans

Hello everyone,

I use adobe scan for note taking on my iPad. I will scan images of my whiteboards and really have loved organizing my notes like this. However, recently it is not allowing me to modify scans after I have saved them. It tells me that it is unable to modify because the scans have been modified outside of adobe scan. However, I haven't been modifying them outside of the app or anything. This makes it way more difficult to save a section of notes and then add to it later without having to remake a new scan and combining everything. Does anyone know how I can resolve this issue?