My first thoughts are key fob battery. Anyone know otherwise?

 

It requires 2 or more presses of the fob's lock to lock, but only 1 press to unlock.

I would guess that the button is simply worn

I would agree with that analysis. It recently happened with my wife's 18 year old Avensis. The dealer quoted £250 to get a new key and program everything up so that it'd work.  She went somewhere else and bought a new car instead.

I would agree with that analysis. It recently happened with my wife's 18 year old Avensis. The dealer quoted £250 to get a new key and program everything up so that it'd work.  She went somewhere else and bought a new car instead.

 

 

 

That's mental. These old fobs can be programmed as they're distinct from the key. Just need the right shape key

 

Thanks for the input you two