open_mfdataset parallel=True failing with netcdf4 >= 1.6.1

What happened?

When using the parallel=True key, open_mfdataset fails with NetCDF: Unknown file format. Running the same command again (with try+except), or with parallel=False executes as expected.

works:

xr.open_mfdataset(dirpath +'\\*.nc', parallel=False)

works:

try:
   xr.open_mfdataset(dirpath +'\\*.nc', parallel=True)
except:
   xr.open_mfdataset(dirpath +'\\*.nc', parallel=True)

fails:

xr.open_mfdataset(dirpath +'\\*.nc', parallel=True)

[Errno -51] NetCDF: Unknown file format

all with engine='netcdf4'
any help is highly appreciated as I'm a bit lost how to investigate this further.

What did you expect to happen?

No response

Minimal Complete Verifiable Example

No response

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

No response

Anything else we need to know?

No response

Environment

Start by reproducing the failure with xarray.open_mfdataset using parallel=True and engine='netcdf4', then compare it with parallel=False and the retry behavior described in the issue. The issue provides no file, test, traceback, or environment details, so done would require identifying the cause and adding a regression test that covers the failing parallel case.