To reproduce:

$ emacs -Q
C-\ russian-computer RET
[turn Caps Lock on]
абвгдеёжзийклмнопрстуфхцчшщъыьэюя

I get some letters (namely б, ё, ж, х, ъ, э and ю) in lower case
instead of the expected upper case.  At the same time, (uppercase
"абвгдеёжзийклмнопрстуфхцчшщъыьэюя") does produce the expected
result.

Paul