Hello Warpslide!
There are some UTF-8 characters in there that Mystic can't display.  You could try converting it to CP437 with iconv:
iconv -f UTF8 -t CP437//TRANSLIT CRYPTOGM.TMP > CRYPTOGM.TXT
Btw, busybox has iconv.  Cool.  There are quite a few encodings  
supported.
busybox iconv --help
BusyBox v1.37.0-FRP-5398-g89ae34445 (2024-06-25 08:38:11 BST)
Usage: iconv [-lc] [-o outfile] [-f from-enc] [-t to-enc] [FILE]...
Convert text between character encodings
    -l  List all known character encodings
    -c  Silently discard characters that cannot be converted
    -o  Use outfile for output
    -f  Use from-enc for input characters
    -t  Use to-enc for output characters
-- 
  ../|ug
--- OpenXP 5.0.58
 * Origin: (} Pointy McPointface (618:250/1.9)