Debug what caused spark job to fail

[damccorm]

Trying to root cause #36346 (comment) in a CI environment

With all GBEK changes reverted, this does succeed - https://github.com/apache/beam/actions/runs/18381522753/job/52368896343?pr=36454

After reapplying c4b2f19 it fails again - https://github.com/apache/beam/actions/runs/18385306114/job/52382127110

Interestingly, limiting it to just 1 test running at a time causes the job to succeed. So I suspect this is a test issue - https://github.com/apache/beam/actions/runs/18388238231

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 36.21%. Comparing base (e3293e2) to head (867f9d6).
⚠️ Report is 8 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #36454       +/-   ##
=============================================
- Coverage     55.03%   36.21%   -18.82%     
  Complexity     1667     1667               
=============================================
  Files          1058     1058               
  Lines        165248   165285       +37     
  Branches       1190     1190               
=============================================
- Hits          90940    59865    -31075     
- Misses        72134   103246    +31112     
  Partials       2174     2174               

Flag	Coverage Δ
python	40.53% <ø> (-40.41%)	⬇️

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[damccorm]

Fixed in #36479