OK, I believe to have been able to reproduce the reported issue and identified the likely "culprit":
ali@mini:~$ dmesg | grep segfaultwhich is most likely a consequence of line 17 in '/etc/init.d/tc-config': echo "$USER":tcuser | /usr/sbin/chpasswd -m
chpasswd: segfault at 8000000 ip b76a1839 sp bfaebecc error 4 in libc-2.11.1.so[b7632000+13d000]
As the same could be found in MC 3.8.2 (but not in MC 3.8.1) I'm pretty sure that means a regression in BusyBox v1.19.0 for the 'chpasswd' applet.
To which degree this segmentation fault is having a negative impact is something I can't tell for sure. At least as the "Password for 'ali' changed" message appears and '/etc/shadow' has indeed been updated I suspect the fault stems from the few "cleanup" statements following in the source code after that message has been printed. So I personally would not worry too much, but there is always the option to fall back to MC 3.8.1 (or earlier) where an older versions of BusyBox was used.