I have this problem too since I upgraded to windows 10. (1) the custom hotkey disappear frequently and I have to go to advance setting to reconfigure which drove me crazy
(2) the custom hotkey doesn't work some time for some languages such as switching back to English from Chinese Cheong Jie , am on Asian IMEs as well so I have a strong feeling as you.
I have just read ToroLuke's today, and I have applied it just now. Did you confirm both (1) and (2) cannot be fixed by ToroLuke's solution or just (2) as a new issue ?