If I am reading the screen shot correctly, it appears March 7, 2018 was the last good fdata/fdata0?
I am curious if it’s the data or wxsim lite.
You may have already tired, but my first attempt to correct the issue would be to change my NAM FOUS site to http://tgftp.nws.noaa.gov…etc, & download to see if this helps in obtaining recent model data.
Second, try opening wxsim and go to auto run & other settings , open up the mixed wxsim-lite box & uncheck Use bias-corrected model data.
Rerun wxsim and see if it completes without any errors. This might indicated the issue is with wxsim-lite fdata?
Just a thought…