Toyota Yaris YRX power steering Assy jamming

[kimona]

A new Yarisworld member wrote me with this concern. Can anyone help him?

Toyota Yaris YRX power steering Assy jamming

Dear Sir,
I have a Toyota Yaris YRX , Sedan -2007 Model Auto , last couple of days every time I want to try doing reverse parking the power steering stiffens up , can’t turn the wheel as a power steering would normally work , also noticed it jams up while trying to do reverse parking & loosens up in driving forward , a similar condition happened in 2015 , where upon continuous persisting with the Toyota dealers in Western Australia, about the fault their diagnosis didn’t show anything , I even got charged heavily for this , also similar situation this time , In 2015 they finally changed a part in the power steering assembly and it has worked fine until last few days same problem has re occurred, can some one please help why this is happening?? Also I go to a Toyota dealership & they are unable to diagnose the fault & just charge for finding nothing, please note this situation is unfortunately happening on & off at random & not consistently.
Can some one please assist how to rectify this situation.