Hi. I have the same exact problem on my HP notebook too for the past year and a half or so!
I didn't bother to solve it before, but now that I read your post that got me thinking about it. Since you r facing the same problem I figure it could be an HP setting.
One most likely setting could be related to continuous holding of keyboard button. I recall most computers have such a setting about whether the button should repeat the signal and at what rate/speed. So hopefully fiddling with this setting should resolve this issue.
Not sure where this setting is, it could be in the BIOS even. Will check when I have a chance and update you if you don't find it before I do.
Thanks.