Command block text field deletes all text when pressing "a" on keyboard

When typing in the command block GUI, all text is sometimes deleted after presing a certain key on the keyboard. (Mostly the "A" key).

Expected result: The letter a gets put into the text field like every other character

Actual result: When pressing a, all of the text in the text field gets cleared and the letter a gets put in.

Steps to reproduce: 1. Place a command block

                                   2.Input any command, or other text

                                   3.Press the "a" key on the keyboard

                                  4. Everything in the text field is gone

Note: I cannot reproduce this bug consistantly! It happens sometimes, but not every time I hit the "a" key. Therefore I can't give further details. I am using a european keyboard and can confirm that this only happens in Minecraft and no other applications.