Question PC starts onlyfrom shorting the 24pin

[CoCo98]

Hi, today i find out that my pc won't start from power button, neither front the mobo pins. The psu passed the paperclip test so i tought It could be a mobo issue buy I noticed that if I try the paperclip test while the 24 pin is inserted in the mobo everything comes to life and I can turn on the pc from the power button. The pc works fine exept that if I put It in sleep mode it actually turns off. I've also noticed that actually the pc some time starts while i force the cable pins and press the power button, even if the pins are not loose at all. For this reasons i think it should be the 24 pin cable buy i'd like ti have other opinione, thanks