I had similar issues to what you are describing with yours on my original unlocked/unbranded HOX on T-Mobile. I had issues on top of the ones you mentioned where it was also saying I had a signal and had appeared to lock up and would just drop the mobile network and say at the bottomg of the screen "preparing sim".
Most the time I was stuck with putting it in and out of airplane mode to make calls, only for them to drop or fail all together.
This was on both 1.26 and 1.28 FW. In the end I took mine back and swapped it and the replacement has been perfect since. so it was without doubt a hardware fault in my case!
Good luck solving your problem, but I would suggest taking it back and getting a straight swap.