LG G3 - Miracast Android 6.0

Miracast recently stopped working on my LG G3 (LG-D852 - 32GB), stock 6.0. My phone goes through the connection process, mirrors the very top of the screen for a split second, and immediately disconnects. I initially thought this was due to the Marshmallow update, as it worked before that and hadn't tried it since the update. I tried the following to troubleshoot the issue:

1. I tried a device at a friend's house - no luck.
2. Same friend's girlfriend had a G3 with 6.0 - Miracast worked on her phone.
3. I tried safe mode - no luck. However, instead of the flash of the top of my screen, my phone "thinks" it's connected to the device. However, nothing shows up on the TV screen.
4. I did a factory reset and tried again - no luck.

Finally, I thought it must be hardware. I sent the phone back under warranty. They replaced some stuff and sent the phone back "repaired". I came home and tried it before doing anything else to the phone. Miracast worked. I went to restore my stuff but noticed the phone was now on 5.0.1. I updated to 6.0 and am back to the same issue.

So, I'm back to it being a software issue. However, how can the software issue exist with my phone but not with my friend's girlfriend's phone? We are also using the same carrier. Does anyone have any ideas?

Thanks in advance