The latest syscheck should have a check for 253 nand emulator from sorgelig as well.
I created my own 253 to launch armboot.bin from the bootsnk folder instead of the bootmii folder, and it crashed on that one
as well. I had 2 add 1 additional check in the program sys.c file, and it worked again.
So, give it a little credit, it does produce some very usefull information, and if it crashes, it's not a random issue. It's very logical.
It could perhaps use a little improvement and should perhaps ask if it should check an ios above 250 with an unknown version.
(And warning you that it might hang upon that check.)