Could be any number of things my friend, for example, do you have a DWO (Date Wheel Overlay) fitted?
Is the date wheel kinked, out of profile? All teeth good?
Is the channel that the date wheel rotates free of dirt, hairs, grease, oil, dust, or any foreign bodies?
Then there's individual components to check, but like anything in watchmaking, its all a process of elimination unless you are about to completely strip down to fully service, then even after that, each and every part, pivot, jewel has to be checked to ensure everything is as it should be and not missing, broke, or worn.