We ended up putting a new ram, promblem solved, thanks for your replies!

The realignment procedure is,
put into sideways mode, then steer fully anticlockwise as far as it will go making sure both front steering rams are fully extended, then put back into forward mode. There is a small valve on the piston of the right hand ram used for equalising the cylinders, this maybe leaking and allowing the oil to cross from one side of the cylinder to the other, worth checking.
Steve.

Thanks for the replies guys,

This fault occurs when driving straight, the right hand wheel drifts off to the right. I've stripped the cylinder but I can't see any obvious faults with the seals.

how often does this happen?
this is a common problem combilift machines have after changing steering modes repeatedly. Over a period of time the wheels tend to get out of sync and they get misaligned.
There is a trick to getting them back in alignment by putting it in sideways mode, steering the wheels full left, full right, then full left and then back to center. After completing this you can change mode back to forward drive and then back to side drive and the wheels should turn and align correctly then.

if this problem is happening frequently as in like everyday then yes, there may be a cylinder leaking internally. There are tests you can do to check the cylinders but for now i would identify what the problem actually is before ordering cylinders.

Is this happening when the machine is sat over night or for an extended length of time?
You cannot swap cylinders to check as they are different, one is a master and the other is a slave.
We have had cylinder glands come loose but you would always have the fault then.
If it is over night it is the cylinder bleeding back, there is no cure for this it is just something they do when left, what you do is put the truck in 90 degree mode steer lock to lock then put back in straight, it should then line up. Later machines have this procedure on a label in the cab.
If the fault reoccurs when using the truck it is something else.

have had cylinders seal fail before could swop over to test check wheel stop bolts are ok , think it needs rhs leg to buffer to overcome valve to send drive wheel round ? if thats not happening , combilift are very helpfull with tech info