LG LG network connection issues- any advice?

[Jeff123816]

I’ve had my T-mobile LG G3 for about a month now. Up until last week, it was working fine. Then, suddenly, a few days ago, I realized that I hadn’t received a call that I was expecting, I looked at my phone and noticed that I had full signal strength and no missed calls/notifications. However, the 4G/LTE indicator was missing. I tried to place a call and couldn’t complete it so I restarted the phone and when it came back up, I received several notifications of text messages and voicemails that had backed up for several hours along with a return of the LTE indicator. Today, this happened again. This time I missed some very important phone calls and texts that were time sensitive. I’m guessing from the messages that my phone was off the network for at least 4 hours before I noticed it. This has occurred in different locations, both of which have very strong T-mobile LTE signals and there’s no indication from the phone of any signal strength issues. T-Mobile is reporting no problems in the area and have advised me to do a hard reset on the phone. I can do this but I’m concerned that it will be an ongoing problem since my phone was factory fresh only a month ago. Is there anything else that I can look into? I’m seriously thinking of selling this phone before it drops significantly in value.
Thanks!

 

[B. Diddy]

I wonder if it could be a problem with the SIM card. Ask T-Mobile if you can try a replacement.

 

[Jeff123816]

So I gave it a try but the problem continued. I finally did a factory reset, which seems to have fixed the problem (at least, it hasn't recurred in the last couple of days. Unfortunately, now my battery is draining like crazy... it was really good before I did the factory reset but now I'm seeing "Android System" running wild. It's dropping about one percentage point every minute or so... I don't understand why, as I restored from Google play without installing anything that wasn't already there. I know the "Android System" thing has been a long standing mystery... is there anything that I should be specifically be looking at? I run Greenify (which I did before the restore) and that seems to have always been successful.