This is the underlying cause of the bug that @JuanCab was seeing. It appears if a reduction step cell (e.g. calibrating dark images) is executed before the masters needed for that step have been created (and they may extend to executing the dark calibration cell before the previous master_bias creating cell has finished executing, not sure).
As a result, the image collection does not know about the master even though the master exists in the folder.
This is the underlying cause of the bug that @JuanCab was seeing. It appears if a reduction step cell (e.g. calibrating dark images) is executed before the masters needed for that step have been created (and they may extend to executing the dark calibration cell before the previous master_bias creating cell has finished executing, not sure).
As a result, the image collection does not know about the master even though the master exists in the folder.