Albeit now 2 years later, still finding little on this problem posted by others.
We encounter this situation periodically -- also on Macs under OSX as
recent as 10.11.6 -- with the only common denominator being maybe
heavy system load. All language-based data entry configuration is correct.
Seems like the CPU cannot keep up with typing speed, and the most recent
character is given higher priority processing than what came before, probably
resulting from a hack in trying to appear responsive to the user, inverting the
order in which characters are received by the application. Just guessing.
Frustrating it has not been fixed even after many years.