Clean up ZIM FAILED status and add test

[audiodude]

Fixes #654.

[codecov]

Codecov Report

Patch and project coverage have no change.

Comparison is base (dd77154) 96.34% compared to head (579cb08) 96.34%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #656   +/-   ##
=======================================
  Coverage   96.34%   96.34%           
=======================================
  Files         100      100           
  Lines        7831     7831           
=======================================
  Hits         7545     7545           
  Misses        286      286           

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