Especially when getting tons of text in group mms or scrolling in a group mms it starts to seriously lag and freeze. Tons of lag. It's horrible. When switching the app to textra 0% lag. The phone runs flawless.
I use Textra simply because the stock app is so hard to use because of all the lag. It makes it very hard to enjoy the phone. The HTC one was similar. So it's probably an underlying android problem.
I'm not noticing any issues with mine- as a matter of fact I was happy to get rid of Go SMS to text my softball team groups. I'm a Verizon customer. Is it possible it is a carrier issue?