Though I notice that you are using 'exposure blending' output, but hugin has only identified 5 stacks out of 60.
With 'exposure blending' each image is passed through enfuse, which among other things removes any cropped_tiff offsets. This will increase memory usage, if you don't want exposure blending then you will get better results using 'normal' output.
This does look like a memory leak in enblend.
Though I notice that you are using 'exposure blending' output, but hugin has only identified 5 stacks out of 60.
With 'exposure blending' each image is passed through enfuse, which among other things removes any cropped_tiff offsets. This will increase memory usage, if you don't want exposure blending then you will get better results using 'normal' output.