I originally was running stock, but fully rooted, S-Off. I've since switched to trying AOKP and now I've settled on Sinless GPe 3.4.7. I have not seen any real difference between them as far as getting a good connection to the network. I started switching ROMs well after I've noticed an issue, and I have not done much of anything to my phone in the last few weeks that I could attribute to the change. I've never dropped the phone or damaged it in any way.
I just recently traveled across the state and would run speedtests next to my wife's iPhone 5c and 19/20 times she'd show full bars with LTE service while I was either on 3G or no service at all. My phone will connect to 4G sometimes though, it's just not that often.
I read that there may be an issue with my SIM card, so I stopped in and had it replaced. The guy seemed very confused about the state of my phone software, so he blamed any issue I was having on the software installed. Regardless I did get a new SIM card installed. It did not seem to help at all. Can anybody help me? I'd hope to not have to go through the hassle of attempting to get the phone replaced!
After rebooting my phone, my phone locked to an LTE signal at -112dBm. It does not speed test at over 3Mbps. Testing my wife's iPhone shows her at -100dBm and she was able to pull 30Mbps down.