Something wrong with dataset "crayon"

When reconstructing the whole dataset "crayon" on scisoft13, the following files are created:

rec_0000.hdf5
rec_0322.hdf5
rec_0644.hdf5
rec_0966.hdf5

The file rec_0644.hdf5 contains a reconstruction with strong ring-like artefacts. It is certainly a flat-field issue. The previous stages do not have this issue, nor has the last one (but the last is created with a new Pipeline instance).

The problem also occurs when phase retrieval is off.

Click to see the reconstruction log

Going to reconstruct slices (0, 999)
Processing sub-volume (0, 336)
Creating a new pipeline object
Data shape for flatfield is (1500, 336, 2048)
Data shape for phase is (336, 2048)
/usr/lib/x86_64-linux-gnu/libcublas.so.9.1
libcublas.so.9.1
Data shape for take_log is (1500, 322, 2048)
Data shape for build_sino is (1500, 322, 2048)
Allocating recs: (322, 2048, 2048)
Data shape for reconstruction is (1500, 2048)
Creating directory /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec
Reading data
Region = (None, None, 0, 336)
End Reading data
Transfering radios to GPU
Allocating radios: (1500, 336, 2048)
Applying flat-field
End Applying flat-field
Performing phase retrieval
End Performing phase retrieval
Reshaping radios from (1500, 336, 2048) to (1500, 322, 2048)
Taking logarithm
End Taking logarithm
Building sinograms
End Building sinograms
Reconstruction
End Reconstruction
Getting reconstructions from GPU
Saving data
Wrote /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec/rec_0000.hdf5
End Saving data
Processing sub-volume (308, 658)
Destroying pipeline instance and releasing memory
Creating a new pipeline object
Data shape for flatfield is (1500, 350, 2048)
Data shape for phase is (350, 2048)
Data shape for take_log is (1500, 322, 2048)
Data shape for build_sino is (1500, 322, 2048)
Allocating recs: (322, 2048, 2048)
Data shape for reconstruction is (1500, 2048)
Reading data
Region = (None, None, 308, 658)
End Reading data
Transfering radios to GPU
Allocating radios: (1500, 350, 2048)
Applying flat-field
End Applying flat-field
Performing phase retrieval
End Performing phase retrieval
Reshaping radios from (1500, 350, 2048) to (1500, 322, 2048)
Taking logarithm
End Taking logarithm
Building sinograms
End Building sinograms
Reconstruction
End Reconstruction
Getting reconstructions from GPU
Saving data
Wrote /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec/rec_0322.hdf5
End Saving data
Processing sub-volume (630, 980)
Reading data
Region = (None, None, 630, 980)
End Reading data
Transfering radios to GPU
Applying flat-field
End Applying flat-field
Performing phase retrieval
End Performing phase retrieval
Reshaping radios from (1500, 350, 2048) to (1500, 322, 2048)
Taking logarithm
End Taking logarithm
Building sinograms
End Building sinograms
Reconstruction
End Reconstruction
Getting reconstructions from GPU
Saving data
Wrote /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec/rec_0644.hdf5
End Saving data
Processing sub-volume (952, 1000)
Destroying pipeline instance and releasing memory
Creating a new pipeline object
Data shape for flatfield is (1500, 48, 2048)
Data shape for phase is (48, 2048)
Data shape for take_log is (1500, 34, 2048)
Data shape for build_sino is (1500, 34, 2048)
Allocating recs: (34, 2048, 2048)
Data shape for reconstruction is (1500, 2048)
Reading data
Region = (None, None, 952, 1000)
End Reading data
Transfering radios to GPU
Allocating radios: (1500, 48, 2048)
Applying flat-field
End Applying flat-field
Performing phase retrieval
End Performing phase retrieval
Reshaping radios from (1500, 48, 2048) to (1500, 34, 2048)
Taking logarithm
End Taking logarithm
Building sinograms
End Building sinograms
Reconstruction
End Reconstruction
Getting reconstructions from GPU
Saving data
Wrote /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec/rec_0966.hdf5
End Saving data
Merging reconstructions to /scisoft/users/paleo/data/id19/crayon/nabu_rec/rec.hdf5