What I did:
Scanned multiple pages documents. Most of the time, I scan only a few pages and it works smoothly.
But I realized that when I want to scan a bigger document (I guess more than 8 or 10 pages), the app crashes. It happened a few times in the last months. I remember at least two or three times that I tried to reopen the app and rescan everything, but the app would crash one more time.
Now when I have to scan something big, I use Adobe Scan or Scannable and paste the PDF in Agenda. If the document is only a few pages long, I use the scanner in Agenda.
Things that might be helpful to know (Agenda version, OS and model, etc):
iOS 13 (last version available)
Latest version of Agenda