LGot an issue with keys in my 1999 Discovery II TDI

Got the an issue with keys in my 1999 Discovery II TDI

1. One Key has lost its buttons so it won't open the doors
2. One key (which I bought new last year) has stopped working

STEP 1
With number 1 key I open the door with the key and the alarm goes off
Put the key in the ignition and the immobiliser light goes out and car starts.

STEP 2
Changed the battery in number 2 key,
Tried to open doors with buttons nothing
Tried to open the door with key alarm goes off.
Put key in ignition alarm continues and immobiliser light stays on
Put number 1 key in ignition, alarm stops, immobiliser stays on

Only way to get out of this one is to disconnect the battery then back to step 1.

If I stop the car for any period of time I'm back to step 1

HELPPP!