Layout switch unwanted combination Rshift+Lshift

[Pavel]

Ubuntu 18.04.1 LTS
Linux version 4.15.0-33-generic

WHAT I EXPECT TO HAPPEN:
"R-Shift + L-Shift" hotkey combination doesn't change keyboard layout when not configured to do so.

WHAT HAPPENS INSTEAD:
"R-Shift + L-Shift" changes keyboard layout even when not configured to do so.

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My machine is set up to use "L-Alt + L-Shift" combination for switching keyboard layout between English and Russian. The command I use to configure this combination:

gsettings set org.gnome.desktop.input-sources xkb-options "['grp:lalt_lshift_toggle']"

With this setting Ubuntu also reacts to "R-Shift + L-Shift" combination and switches the layout as well. This is very irritating, since when typing the C code I often need to use macros like MY_MACRO_WITH_UNDERSCORE, where I naturally hit both shift keys when typing a capital letter after an underscore. The issue appears only when the R-Shift is hit before the L-Shift and not the other way around. The issue doesn't appear when I disable my switch combination with:

gsettings set org.gnome.desktop.input-sources xkb-options "['']"

I also disabled default Super+Space and Super+Shift+Space combinations, although that doesn't affect the issue. I didn't set any other keyboard combinations for switching layouts. The issue appears both in the terminal and in GUI applications.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Alex Rudenko (alexei-rudenko)]

It seems like whether lshift + rshift changes the layout depends on the other set combination. For example, changing keyboard layout on Left Alt would disable lshift + rshift as well as removing all switch combinations.

[Alex Rudenko (alexei-rudenko)]

Also, Alt + Shift would enable LShift + RShift whereas Left Alt + Left Shift would not.