This document is incomplete
The error 13 is displayed by the initial installer. It can be see in logs as well as in the web installer. By itself it means nothing, despite being labeled as "Image corrupted" (suggesting that PAT file is the culprit). However, in reality the error 13 means "something went wrong with the installation".
To diagnose the culprit one needs to check:
dmesgfor any shimming or mfgBIOS errors/var/log/messagesfor any signs of firmware update, or (most likely) problems with Synoboot shimming/var/log/junior_reasonto see why the installer even appeared