Latitude C Series Function Keys

So I pretty much fixed up an old Latitude C610 (fixed one for two broken ones).

It seems to be working almost perfectly despite being completely rebuilt.

However I am having a problem with the function keys. I understand that there is no Dell Quickset for this system however instead installed 3RVX which works fine.

However two of the keys (Fn and Page Dn, Volume Down & Fn and ↑, Brightness Up) do not work. When they are pressed I get a ding noise. 

The Page Down and the Down Arrow Key both work normally however.

There are no errors in the device manager. I had a look through BIOs settings but couldn't find anything to help me, I also updated it to A16.