Weak GSM singal after updating Android OS

[JJHarding]

After updating my Sony Xperia M5 to Andriod version 6.0 the GSM/ cellphone signal became extremely poor. Testing with another phone on the same network it has good signel but once I use my Sony then the signal drops down to 1/2 bar or to no signal at all.

Please assist?

[tiagogrft]

I just bought one 4 weeks ago, and i have the same problem. Other smartphones had the full signal at the same point where i don´t have anything. I've tested with the same SIM card. So my camera can't focus about a meter distance, I've tested many situations, the only way is setting the manual mode and and landscape scene. The battery is awful, my 2013 old phone running the same apps lasted more than half. I did all the software repair, with xperia companion, contacting the support. Now i'll have to send it to warranty. Very upset about this.