I've just got help with an associated issue, and I guess it may be useful for many of you as well: https://www.neowin.net/forum/topic/1261058-windows-81-is-forgetting-ctrl12345-shortcuts-designated-for-keyboard-layout-switching-after-wa/
Windows seems to overwrite personal layout controls configuration with defaults on some occasions. Hence what, the way to have a "permanent" solution basically appears to be is rewriting your
HKEY_USERS.DEFAULT\Control Panel\Input Method\Hot KeysHKEY_USERS\.DEFAULT\Control Panel\Input Method\Hot Keys
with what you have in your
HKEY_CURRENT_USER\Control Panel\Input Method\Hot KeysHKEY_CURRENT_USER\Control Panel\Input Method\Hot Keys
once you've configured your IME shortcuts (or in this matter their absenсe) correctly.