So since there is not a specific thread listing all the problems of the marshmallow update, I figured I would make one. You all can add your problems in here too. This way the tmobile folks can address these issues quickly and send out an update to fix.
For me, so far I have the following issues.
1. When using google hangouts, I am having audio issues with people not hearing me at all during video chat. To fix I need to keep ending the video chat, and starting a new one until the audio works. Second, when I am using the camera to face me, and then I want to switch to the main camera on the back of the phone, this does not work at all. The image freezes for the person on the other end. Then when switching back to the camera that faces me, it does not change from the frozen image on the other end. So I need to disconnect the video chat and then reconnect.
2. In the stock text messenger app, and hitting the attachment icon in a text, to take a picture directly to send, there is no longer an option to turn on the flash directly from this shortcut before sending the picture message. If it is dark, there is no way to turn on the flash. Only fix to this is to go into the camera app, then take a picture with the flash on, and then go back to the messenger app, and add the picture to the text and send. This is not a huge issue, but its still annoying to have to go back and forth like that. Prior to the update you were able to turn on the flash directly from the stock text messenger app.
3. Group texts no longer work. I can create a group and send a text to said group and it'll show up on each participants end as a direct text. They won't see any of the other people in the group, it'll look just the same as if I texted them directly. And when they reply it'll be a direct text as well. It doesn't show their texts in the group at all.