Nokia Lumia :: 900 Gets Stuck On 4G (HSPA+) And Won't Connection?

In this thread, 4G referrs to HSPA+, LTE referrs to LTE.Below I'm going to go into detail about the LTE issue with the Lumia 900 on AT&T. This issue is separate from the no data connectivity issue that has already been addressed with an update.The problem: The phone will not reconnect to LTE after you leave the LTE coverage area and come back into the LTE coverage area. Data works fine, but the phone only connects to 4G (HSPA+). You are now stuck with slower 4G untill you reboot the phone or use the airplane mode trick (explained later).For example: I live in a 4G coverage area and work in an LTE coverage area. I go to work and the phone connects to LTE. I go home and the phone drops to 4G like it should since there is no LTE there. When I go back to work the next day, the phone will not connect to LTE. It stays on 4G. I have attached two pictures demonstrating the issue. Picture 1 shows the phone with a 4G data connection even though I have 5 signal bars and I'm in an LTE coverage area. Picture 2 shows the same phone after I reboot the device. I'm in the exact same location, but I now have LTE after reboot.

When does the problem seem to occur? The problem occurs if you leave the LTE coverage area and come back after a few hours. It seems to happen most often after only 2 to 8 hours in the 4G area.I have been working with AT&T engineering for about a month and they have done multiple traces and can't find anything wrong with the network. They see the phone connected to the 4G antenna instead of the LTE antenna on the tower. My moms Lumia 900 has the same problem. My wife has the HTC Titan II Windows Phone with LTE and it works perfectly.Based on my own observations, the issue has nothing to do with the amount of data you use either. During the time you leave the LTE area, the battery may also appear to drain faster than normal. I believe the problem is the phone keeps looking for that LTE signal but can't find it. It then gives up and goes into 4G mode to save the battery but never again tries to reconnect to LTE.

How to force create the problem: I did this 8 miles from the official LTE coverage area. 1) At a high elevation facing the LTE coverage area, I turned on airplane mode while I was NOT in the LTE coverage area. 2) Next I turned off airplane mode. 3) The phone connected to LTE with one signal bar while not in the LTE coverage area. 4) Moments later it dropped to 4G. 5) Then I drove 10 minutes to the LTE coverage area and it did not connect to LTE. It appears the phone saw the very weak signal and locked itself in 4G mode.Temporary fix: To restore the LTE connection, you can reboot the device, or turn airplane mode on and then turn airplane mode off a few seconds later. This of course turns off all radios and turns them back on.