Which product do you try to resample? Can you post the name? Have you tried to use DIMAP as output format? Is this working and is the result multi-size?
I remember there was some problem when storing resampled S2 to GeoTiff. But this should have been fixed in version 6.
have you tried the graph I provided here:
This once worked. In the Graph file you can switch to Big-GeoTiff format.
In the header of the graph is an example call shown.