Other factors for a plateau or form slip when increasing the weight could be due to a simple thing like imbalances and/or tightness in certain areas. The best way to fix this is to find out what the root cause of this is and working on corrective exercises and/or a good stretch routine aimed at fixing it!
Always remember that it's not always about the weight, because your muscles don't know what the numbers on your plates! So focus less on that and more on perfect execution.
Hybrid Training Systems