Not sure why I didn’t pick up on this before (I blame August holiday mode!) but if you are getting a 192.168 based address on your device when apparently on bridge mode then you are obviously NOT on bridge mode but still in router mode. My bad for not spotting this!

There are other folks with this problem, as per this thread over at ISPreview…

https://www.ispreview.co.uk/talk/threads/mc801-three...

So not your VLAN setup at fault but the ZTE firmware has some bugs!! Try some of the workarounds or factory reset the ZTE to see if that helps, before putting it into bridge mode.