Ok thanks it sounds as though the best thing will be to wait until an engineer is carrying out repairs/maintenance and see if we can get the problem sorted.
Another issue with these machines that you may be able to help with is that on one of them if you open the main doors during programme either at an M00 or in single block to check the part etc, when you re-shut the doors you can just press 'cycle start' and continue the programme, however with the other machine you have to press the 'feed start' and 'spindle start' buttons before pressing 'cycle start'.
Is this also due to this PLC set up that you've mentioned and something that would have to be altered by a machine engineer?