$ perl -e 'printf "%08b\n",ord("5");'
00110101
$ perl -e 'printf "%08b\n",ord("k");'
01101011
$ perl -e 'printf "%08b\n",ord("8");'
00111000
$ perl -e 'printf "%08b\n",ord("Z");'
01011010
Strange. Seems more than a simple bit flip. I haven’t seen this myself, or heard of it much from other users.