I purchased three DS-2CD3320D-I cameras (firmware: v5.3.1) when I was in China last month, without realizing any region code issues. Luckily, when the first one being hooked up to an existing LST system, there was no issues at all (except week display in Chinese). After a couple of days, when installing the 2nd and 3rd cameras, these cameras simply did not connect at all. Moreover, the 1st one (Chinese version) stopped working as well. Very, frustrating!
About to give up, after several days, I was making my final effort, all of a sudden, the 2nd and 3rd got connected mysteriously! Very unbelievable! I still don't know what happened. However, the 1st one is still unable to connect to the LTS NVR up today. Very weird...