CTRL+SHIFT+??? also changes language, when just CTRL+SHIFT should do it

It is known ugly bug - see launchpad bug 1245473.

I'm writing this from Ubuntu 16.04.3 LTS with MATE DE. It does not have this problem.
I'm using Ctrl+Shift layout switcher for English and Russian languages.
I see no interference here.

But MATE on Ubuntu 17.10 and 18.04 LTS has this problem - see other launchpad bug 1720364.