Key battery keeps dying

[Dannyboolahlah]

I've had my A4 for about a month now. Key didn't work when I got it, changed the batteries and synced it, then it worked fine for about 3 weeks. Then stopped. Changed them again and it's lasted 2 days and about 3 uses before dying again.
Is there anything that could cause this or is the key knackered?

 

[Pops848]

What quality are the batteries?

I got some Duracell and still going strong

 

[Dannyboolahlah]

First lot were Duracell. Second lot were Grundig.

 

[QuattroCalum]

Sounds like one of the buttons are jammed, take it apart and clean it, see if there are any sticky buttons.

 

[Dannyboolahlah]

Have done. All looks fine. Buttons seem to press and pop out again as they should.
I've bought a new key now, was hoping to just swap the blade over from the broken key but realised you need a 2 keys to programme it