Getting potential from fusing rate lowered?

It seems that when fusing two clean items (non-potential) together, the chance to get potential has been decreased. Before any patch or server check (haven't been fusing for three days(?)) I managed to easily get 5-6 shoes with hidden potential. I'm current fusing and I'm very lucky to obtain 2-3 shoes with potential. I doubt I'm that unlucky, because so far I did four inventories and the rates are pretty much the same every time...

Any ideas on what happened? I'm fusing Blue Sneaker Shoes (level 31).