@Justin Thank you for reaching out to Microsoft Q&A. I understand that you are having issues with random disconnects from P2S VPN from some users and not all of them. I also see that you are getting a Idle Timeout with error828.
Upon further investigation regading this Error 828, it looks like if the "IdleDisconnectSeconds" option is set to 0 the timeout is disabled as per this document.
When I connect from my machine via P2S, I see this timeout option is set to "never" in my PC thus never triggering this value. Here is a snapshot of the same:
Can you confirm if you see anything different in these couple of machines that are disconnecting for the "IdleDisconnectSeconds"? Thank you!