st2000dl001 sticktion ?

hello ,

i have got a st2000dl001 that has a head stiktion , "when connected to ddi4 it gave the sound of sticktion and i powered it off after less than 10secs"

i opened the hdd cover in a clean room the head assembly was sticked into the middle of the platters .and smoothly moved the heads into their park along with slowly rotating the platters .
heads parked smoothly and no damage was done to the platters , but one thing that prevent the hdd from working is that after powering on the drive , the heads doesn't move freely on the platters "saw that only once to prevent damage", just like they have lost their original place , and they stop right on the platters edge .

the heads assembly has no visual damage to identify the contact point between them and the platters .

any ideas ? thank you