after wake-up: 4 tabs to password

since about two months I have a peculiarity. After wake up by a key press I need to type 4 tabs to get the password field to appear and to get the focus. The initial wake up key and and any other characters but tab, have no further effect at all. It is not a big thing, because pressing 4 tabs is quickly done... But, can anybody please explain to me what is happening, and, maybe, how I can revert to the 'normal' login? What I consider normal, is, that the first character typed initiates the wake up, and also appears as the first character in de password field, and that I can continue with the typing of the password. I am on Ubuntu 20.4 and KDE desktop 5.18.8. Thanks in advance! Henk