It seems that your opensees script is trying to import an output file (force.out) before it is fully written. In default, opensees does not finish writing until the process reaches the end of the input script. Alternatively, you can manually force to save your recordings earlier by putting the "remove recorders" command. Please try the revised script and let us know if you still see the problem:
Line 173 added: remove recorders
Line 187 added: set result [lreplace $result end end]
Line 187 is to get rid of the extra newline at the end of the output file.
Thanks,
Sang-ri