Fortran runtime error: Substring out of bounds

I am running a file in fluka. While running the file , a temporary folder will be created in which all the output files are created and once the run is over these output files will be moved back to the parent folder. But in my case, the temporary folder remains there after the run. I’m getting this error in log file.

Fortran runtime error: Substring out of bounds: lower bound (-4) of ‘filpwx’ is less than one

Error termination. Backtrace:
#0 0x7fd7b1209aed in ???
#1 0x7fd7b120a605 in ???
#2 0x7fd7b120ac72 in ???
#3 0x559536d4535c in pwxsrd_
at /home/alfredo/fluprogfor/pwxsmvax/pwxsrd.f:93
#4 0x559536c7eaf9 in xsread_
at /home/alfredo/fluprogfor/lowneumvax/xsread.f:1615
#5 0x559536c69554 in lowset_
at /home/alfredo/fluprogfor.2021.2/lowneumvax/lowset.f:295
#6 0x559536c06acb in flinit_
at /home/alfredo/fluprogfor.2021.2/kaskadmvax/flinit.f:175
#7 0x559536ac18b5 in flukam_
at /home/alfredo/fluprogfor/mainmvax/flukam.f:3743
#8 0x5595366ab4a9 in fluka
at /home/alfredo/fluprogfor.2021.2/mainmvax/fluka.f:318
#9 0x5595366ab4a9 in main
at /home/alfredo/fluprogfor.2021.2/mainmvax/(USFLMD):23

Any suggestions why this happens?

Thank you very much in advance.

Hallo, apparently you are not using the official CERN version of FLUKA that is supported on this forum.