AssertionError on very small dir

[TheChief5055]

strace -o /mnt/logs.txt dduper --device /dev/mapper/cachedev_0 --dir /mnt/Exchange --analyze --recurse
Traceback (most recent call last):
File "/usr/sbin/dduper", line 575, in
main(results)
File "/usr/sbin/dduper", line 465, in main
dedupe_dir(results.dir_path, results.dry_run, results.recurse)
File "/usr/sbin/dduper", line 456, in dedupe_dir
dedupe_files(file_list, dry_run)
File "/usr/sbin/dduper", line 410, in dedupe_files
ret = do_dedupe(src_file, dst_file, dry_run)
File "/usr/sbin/dduper", line 224, in do_dedupe
assert len(out1) != 0
AssertionError

Strace log attached.

logs.txt

[bugsyb]

Uploading dduper.strace.log…
Running into the same:

Traceback (most recent call last):
  File "/usr/local/sbin/dduper", line 734, in <module>
    main(results)
  File "/usr/local/sbin/dduper", line 595, in main
    dedupe_dir(results.dir_path, results.dry_run, results.recurse)
  File "/usr/local/sbin/dduper", line 578, in dedupe_dir
    dedupe_files(f, dry_run)
  File "/usr/local/sbin/dduper", line 482, in dedupe_files
    ret = do_dedupe(src_file, dst_file, dry_run)
  File "/usr/local/sbin/dduper", line 293, in do_dedupe
    assert len(out1) != 0
AssertionError

Tried running it in container as privileged, mapped device as well as directly at host level - same error.
It is aarch64.

DEBUG:root:Phase-1: Validating files and creating DB
DEBUG:root:Phase-1.1: Populate records using threads
DEBUG:root:Phase-2: Detecting duplicate files
DEBUG:root:Duplicate files are:
DEBUG:root:[['/mnt/storage-btrfs/dduper-test/storage.tgz', '/mnt/storage-btrfs/dduper-test/1/storage.tgz', '/mnt/storage-btrfs/dduper-test/2/storage.tgz']]
DEBUG:root:Phase-3: Dedupe duplicate files
DEBUG:root:['/mnt/storage-btrfs/dduper-test/storage.tgz', '/mnt/storage-btrfs/dduper-test/1/storage.tgz', '/mnt/storage-btrfs/dduper-test/2/storage.tgz']
DEBUG:root:Phase-1: Validating files and creating DB
DEBUG:root:Phase-1.1: Populate records using threads
DEBUG:root:Phase-2: Detecting duplicate files
DEBUG:root:Duplicate files are:
DEBUG:root:[['/mnt/storage-btrfs/dduper-test/storage.tgz', '/mnt/storage-btrfs/dduper-test/1/storage.tgz', '/mnt/storage-btrfs/dduper-test/2/storage.tgz']]
DEBUG:root:Phase-3: Dedupe duplicate files
DEBUG:root:['/mnt/storage-btrfs/dduper-test/storage.tgz', '/mnt/storage-btrfs/dduper-test/1/storage.tgz', '/mnt/storage-btrfs/dduper-test/2/storage.tgz']