If running under Ubuntu, even some of the native software can't handle keyboard events properly. For example, open 'Text Editor', try to open a file, and in the dialogue search for 'hello world'. Notice that if the system is under load, you will in fact search for 'hdlrow olle'.
This feels like a problem with the Linux desktop stack. Never had this problem neither on macOS nor on Windows. When the system is under heavy load, the events are usually buffered and the app processes them in a quick succession as soon as its UI thread gets to run.
