SWIR output should be set to 0, not to 1.
Currently, the ACwater SWIR output is set to 1, probably, because EnPT used 0 as no-data value so far. However, this changed in https://git.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT/-/merge_requests/98 so that 0 is now a valid pixel value, i.e., ACwater should set the SWIR output to 0 (here).