Due to another bug, I’ve reported, which will turn on a stalker’s flashlight when I switched character.
I generally press right mouse button rapidly, after a silent kill, to hide all the characters before my next step, after a silent kill with enemies nearby.
But sometimes, one of the characters got stuck. I couldn’t switch to him/her by pressing tab button anymore.
Generally, it happened on the second character I’ve tried to hide.
It’s only fixed by teleport to another region.