faulty multi point lock?

I have a UPVC door with Muli Lock system, the Euro Double barrel was just spinning on outside and only locking on the inside. I have repalced the faulty barrel but now the door will still lock one side only and the key will not fully push in on the other side. took the barrel back but it worked ok, I have changed it to the other way round but then locks outside and not inside. The opening turn on the key also seems very stiff?