The issue of the PSP and its troublesome 'square' button has been something of a sticky problem for Sony Computer Entertainment since the launch of the console in Japan.

The fault, which sees the square button on the machine stick down during play, even prompted comment from Ken Kutaragi, who went on record to state, “I didn't want the PSP's LCD screen to become any smaller than this, nor did I want its machine body to become any larger," said the Sony boss. "The button's location is on purpose. It is according to our specifications. This is something that we've created, and this is our specification. There was a clear purpose to it, and it wasn't a mistake.”

However, according to a release from the Japanese PlayStation office this morning, there is a fault. During the manufacturing process, untrimmed resin may be causing buttons to become stuck, a problem which SCEI has now isolated and solved.

The firm is offering to replace the 0.6% of units it claims may be impacted free of charge, and has pledged that any hardware shipped since new year will be sticky button-free.