在 VIM 中搜索的俄语单词中缺少一个字母

Question

当我跑步时：

$ vim -s <(printf '/конфедерация')

VIM 打开并显示'/конфедерция'在左下角，没有'а'.为什么？

'/стол'例如就没有问题。但如果单词稍长，就会漏掉一个字母。英语长单词没有问题。

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.5 LTS
Release:        14.04
Codename:       trusty

Terminal VIM
VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Nov 24 2016 16:43:18)
Included patches: 1-52
Extra patches: 8.0.0056

$ locale
LANG=en_RU.UTF-8
LANGUAGE=en
LC_CTYPE="ru_RU.UTF-8"
LC_NUMERIC="ru_RU.UTF-8"
LC_TIME="ru_RU.UTF-8"
LC_COLLATE="ru_RU.UTF-8"
LC_MONETARY="ru_RU.UTF-8"
LC_MESSAGES="ru_RU.UTF-8"
LC_PAPER="ru_RU.UTF-8"
LC_NAME="ru_RU.UTF-8"
LC_ADDRESS="ru_RU.UTF-8"
LC_TELEPHONE="ru_RU.UTF-8"
LC_MEASUREMENT="ru_RU.UTF-8"
LC_IDENTIFICATION="ru_RU.UTF-8"
LC_ALL=ru_RU.UTF-8

Konsole (Version 2.13.2)

$ echo $TERM
xterm