> To rule out if it was a coding error, I tried to decompress the gzip file with bash via gzip -dc file. bash threw a strange error, “can’t seek file descriptor” when trying to read the file. This error is emitted from bash.c here.

Unless I am reading this wrong, the error would have been emitted by gzip, not bash. There is no redirection or anything here, bash is not even aware of that file.