Maybe you could try to place it into the holder first and use scrcpy to control your phone from your PC afterwards?
Cleaning your device will probably support the general performance. If uninstalling most unused apps isn't enough, a factory reset might help.
WebRTC NACK is Negative Acknowledgement. One of the mechanisms for delivery errors correction in WebRTC. (FIR, PLI, SLI, NACK, etc)
NACK is a way for the receiving party to indicate that it has not received a specific packet or burst of packets. The NACK errors are sent to the sender of the stream, who then decides whether the lost packet will be re-transmitted or not.
Sometimes the sender may choose to send a full video key-frame (I-frame) rather than just a small packet, if a lot of important data is missed for example. Other times it may not choose to send anything if it thinks the packet won't arrive in time to be helpful (perhaps due to high latency).
For whatever reason, the packet loss you are seeing isn't being tolerated all that well, but clearly the system is trying to manage it if there is audio/video drifting. (buffer is trying to adapt)
I'd be curious if this connection was using the TURN video relay servers or not, and if so, which IP address was used. If the connection was peer to peer, lowering the bitrate a lot or using Ethernet instead of wi-fi could help; often does. Even high CPU load can cause issues; try to avoid hitting 100% CPU load a sender. Typically just getting of Wi-Fi fixes the problem.
Other options are to try using 4G LTE or perhaps using apps like Speedify to try to improve connection reliability. &buffer=250 won't work in OBS on PC currently, but would work with the Electron Capture app (or Chrome). The &buffer command can help sometimes with audio drifting, but not always; normally it works best with the desync amount is constant.
If the guest is using a macbook, even plugging in your notebook to a power outlet can improve things, such as audio stutter.
Thank you for your answer!
What issues exactly I am having: we are using restream.io to send the feed to Facebook and YouTube. When I did a test stream earlier, at a couple of points, the video feed went black, and restream did the moving dots thing you also see when it is just starting the feed. I am taking from that that this is a connection issue.
So far, thats the only test stream I have done (yet). I want to make sure we are as free as possible of glitches before I do an actual service with this set up. I will have to run a speedtest (thanks for the links!) tomorrow and see what it says. I'll also check the CPU ussage and see what is happening there.
I'll reply again after I have some more results. :)