First thing Id do is make sure all your cabling is clean and tight.Next check to see if you have an encoder or a set of prox switches on the turret for position ing.
If encoder,with the turret unclamped,rotate the encoder slowly,when you get to an index,the turret should turn.If it goes off on its own,Id look into the encoder.Bad wiring,contaminated glass.
If you have prox switches,make sure they are clean and adjusted correctly.If the turret is hydraulicly driven,you may be able to adjust its speed.
Its also worth looking into the selinoids that decide turret index direction ad the relays that drive them.Nothing is ever clean enough...
This may sound stupid,but is the turret balanced?I had an Ikegai that did weird turret things when it had tools on only the first few stations and none in the last.Good luck and let us know what you come up with.