Comment 2 for bug 1812266

I face the same problem
Keyboard indicator icon keeps disappearing Ubuntu 18.04.1

Gnome shell version 3.28.3 Ubuntu 18.04.1.
As soon as I do screen lock or open up a new application, the keyboard icon keeps disappearing. I have to press super +Tab see the current keyboard layout icon again. But why does it disappear in the first place? I think the problem arose after an update

Here is relevant information from logs:

JS ERROR: Exception in callback for signal: activate: Error: Error invoking IBus.set_global_engine_async: Expected function for callback argument callback, got undefined
setEngine@resource:///org/gnome/shell/misc/ibusManager.js:207:9
wrapper@resource:///org/gnome/gjs/modules/_legacy.js:82:22
activateInputSource@resource:///org/gnome/shell/ui/status/keyboard.js:490:13
JS WARNING: [resource:///org/gnome/shell/ui/keyboard.js 546]: reference to undefined property "_rect"