The issue appears to be related to a buffer management (cache flushing) issue in the exFAT file system driver introduced by Microsoft in all versions of Windows 10 and newer (confirmed for all editions of Windows Servers 2016, 2019, and 2022).
The problem occurs whenever the backup image size exceeds the computer’s available physical RAM. The problem doesn’t happen if exFAT is used inside a NAS device or if the backup destination is set as a network SMB shared folder.
There are no similar issues on other, more popular file systems (NTFS, ReFS, etc.).