Thanks, GK, but sorry, no idea why your msgs would break.
I've tested several keys: both of Enter, Alt, Ctrl, & all the other move keys: Tab, End, Home, etc. No problems.
Possibly the browser, but that's unlikely. I use Firefox & Chrome. I think you mentioned you use IE (Internet Explorer), one I definitely avoid - major dog.
Perhaps your keyboard ? If it's several years old, could be a key switch or the control chip having an occasional fault.
If it's getting grubby, get a new one. They're so cheap now it's not worth cleaning. $10 - $15 here.
However, if you have a laptop, get a can of compressed air & give a blast around the keys.
Turn it off first.