We have two different versions in our fleet THALES and HONEYWELL I think. Some differences eg one allows INIT A page after engine start, one requires heading to be selected before activating secondary flight plan, one puts all changes into the temporary flight plan and requires you to confirm where as one takes the changes straight away, differences in how to change the alternate in flight etc
Have a look at FCOM 4, it may just be a difference rather than a problem.