ZTE has local offices where ever they have equipment to assist support and maintenance. So don’t you have a local office support you? By the way you can use the Signalling trace to see what kind of error you are receiving.
Yes you are right! ZTE support staff have limited experience and knowledge and their R&D have skipped a lot of things in both CDMA and GSM and stopped their development and divert their concentration on 3G . They are in a race of 3G with Western vendors like Ericsson. By the way I have good experience in ZTE GSM their Radio frequency parameters have some bugs that may cause location update problems …etc.