This was reported in Alacritty in alacritty/alacritty#1606.

It seems like when the IME interface is open, winit intercepts all ReceivedCharacter events and instead forwards them to the IME. This works well for applications that rely solely on winit's ReceivedCharacter event to insert text, but it creates problems when characters are inserted as a result of other keyboard events.

There are several solutions for this, winit could for example not send any keyboard events when the IME is open and instead pretend it is a completely separate window. Alternatively, just informing the application about the current IME state would allow at least conditionally disabling keyboard handling when the interface is open.