Found 1 faulty index files, repairing now

This sounds a bit mismatched. If you meant to test all files, see test directions below, and if objective is only the index files (which are smaller, if download time is an issue), ask that way:

Usage: Duplicati.CommandLine.exe test <storage-URL> <samples>
[<options>]

  Verifies integrity of a backup. A random sample of dlist, dindex,
  dblock files is downloaded, decrypted and the content is checked
  against recorded size values and data hashes. <samples> specifies the
  number of samples to be tested. If "all" is specified, all files in
  the backup will be tested. This is a rolling check, i.e. when
  executed another time different samples are verified than in the
  first run. A sample consists of 1 dlist, 1 dindex, 1 dblock.

  --time=<time>
    Checks samples from a specific time.
  --version=<int>
    Checks samples from specific versions. Delimiters are , -
  --full-remote-verification
    Checks the internal structure of each file instead of just verifying
    the file hash
  --full-remote-verification (Enumeration): Activate in-depth
    verification of files
    After a backup is completed, some (dblock, dindex, dlist) files from
    the remote backend are selected for verification. Use this option
    to turn on full verification, which will decrypt the files and
    examine the insides of each volume, instead of simply verifying the
    external hash. If the option --no-backend-verification is set, no
    remote files are verified. This option is automatically set when
    then verification is performed directly. ListAndIndexes is like
    True but only dlist and index volumes are handled.
    * values: True, False, ListAndIndexes, IndexesOnly, IndexOnly
    * default value: False
  --backup-test-percentage (Decimal): The percentage of samples to test
    after a backup
    After a backup is completed, some samples (one sample is 1 dblock, 1
    dindex, and 1 dlist) files from the remote backend are selected for
    verification. Use this option to specify the percentage (between 0
    and 100) of samples to test. If the option --backup-test-samples is
    also provided, the number of samples tested is the maximum implied
    by the two options. If the option --no-backend-verification is
    provided, no remote files are verified.
    * default value: 0.1

Odd if it deletes duplicati-i1e3f08af0c3d449e83bd7af29d3fb5aa.dindex.zip.aes again without failing due to missing file, however similar output could be due to fixing one at a time.

The new manual only documents a few commands itself, but one can search to find old docs:

The TEST command

The other reason the exact same output shouldn’t happen is because sample should change.

Please check the test output carefully to see whether the exactly same files are mentioned.

If you just want a fast and full dindex fix, test all and use IndexesOnly.