PowerBook G4: Letter skipped while typing

I’m using a PowerBook G4 running OS 10.4.11. My keyboard began to fail a while ago. The issue was that Left Cmd-V and Left Shift-R were inop. Since I didn’t know at the time it was a hardware problem, I tried changing some settings. I’ve had the keyboard replaced and the original problem has gone away. But I’m having a problem typing, which started when I tried to fix the other problem. Letters will be skipped. For example, when I typed the title to this thread ‘PowerBook’ came out as ‘PwerBook’. It often happens when I’m typing letter combinations such as ‘er’, ‘io’, or ‘ou’ – combinations where the keys are usually typed in quick succession. Can someone tell me how to fix my keyboard settings so that the keyboard will ‘keep up’?

In System Preferences ==> Keyboard my Key Repeat Rate is set to the fastest setting, and Delay Until Repeat is set to the shortest delay.