I've repeated these exact steps six times with identical results. I've attached crash reports and a screen recording.
Start Publisher 2.0.3 beta
Create a Book
Create a document
Draw a rectangle
Save as Untitled to Downloads (this is the local folder, not iCloud)
Add Chapter - select Untitled and it crashes on open
Affinity Publisher 2 Beta-2022-12-12-101538.ipsAffinity Publisher 2 Beta-2022-12-12-101346.ipsAffinity Publisher 2 Beta-2022-12-12-101256.ipsAffinity Publisher 2 Beta-2022-12-12-101019.ips
Screen Recording 2022-12-12 at 10.20.52 AM.mov