Read: http://forum.xitek.com/thread-1055994-1-1-1.html
(in Chinese, with diagrams)
Actually, the method is more or less the same as the original DIY method but now the "CRC" Contact Cleaner is applied in addition (and then doing the massage) which does help even more, as it is told and confirmed.
After all, the OP has saved $250 (1500 RMB) repair fee as officially quoted and now his DA*16-50's SDM is revived and has been operating smooth and flawlessly! Congrats, man and well done! :-D