Parallel Webpack builds fail to report errors

We've seen this primarily in Azure DevOps linux pipeline agents (doesn't seem to repro on windows), where we have a just task with multiple parallel webpack builds and sometimes there won't be outputs for some of the webpack builds, nor errors. Our just config has something along the lines of this:

series( parallel( webpackCliTask(...), webpackCliTask(...), webpackCliTask(...), webpackCliTask(...), webpackCliTask(...), webpackCliTask(...)), 'postWebpackTask');

The postWebpackTask will still execute in cases where not all of the webpack bundles are observed. Haven't been able to nail down a firm root cause (e.g. is the webpack process dead? do we fail to wait for all of them correctly?)

Start by reproducing the just configuration using parallel webpackCliTask calls followed by series and postWebpackTask on a Linux agent. Observe whether webpack processes exit, whether all outputs appear, and when errors are reported. Done means parallel builds reliably report failures or wait for every expected bundle before postWebpackTask runs.