Help Mercedes w210

[jacostanzo]

Hi mates,
Need any idea about what is the problem on Mercedes w210.
Car came to me with only one key (big motorola key) that unlock esl but ezs never turn.
I have made a new nec key, and worked perfect during 3 days, after that sometimes ezs don't turn but esl unlock.
So I think the problem is not in esl because always lock and unlock well. Any one have an idea?

Thanks