I have two layouts - one for Russian language and second for English. And I use "Ctrl + Shift" shortcut to switch between them. But other shortcuts using "Ctrl + Shift" doesn't work.
For example Opera browser use "Ctrl + Shift + I" shortcut to open developer tools, or Intellij Idea use "Ctrl + Shift + N" shortcut to open class by name. But then I press "Ctrl + Shift" and keep it pressed, layout changes immediately, and the rest of shortcut doesn't work.
Is this bug of KDE? I'm using kubuntu 18.04 and 17.10. Older LTS version of kubuntu doesn't have this issue.

I can confirm this issue. I'm using KDE Neon with KDE 5.12.