Hadn't logged in a while but if that was directed at me, yes. I installed various Plex versions from Apps and from what I remember it happened with the 3 versions I tried. This was only a problem for accessing the initial setup page. All 3 versions seemed to work fine afterwards without any additional tinkering.
I've only been using Unraid for a couple of months and only with 7.0.1 but I briefly had the same issue where I needed to change USB ports every time I rebooted. I'm also at a loss as to why because just as I was going to make a bug report the issue went away. Everything in my DIY NAS is new except for the storage drives. The only 2 things that changed from my initial setup are that as I finished getting my NAS to how I wanted it, I was rebooting it much less than in the initial setup phase where I was rebooting several times a day. It was my first time using Unraid or a NAS so I took a couple of weeks to get comfortable. The problem with the USB suddenly appeared near the end of that phase. The other thing that changed was that the USB was originally plugged into a 2.0 port and right now it's plugged into a 3.2 port.
April 2025 and this is still relevant. I wanted to check out Plex, Emby and Jellyfin to see which one works best for me and my client devices. Happened with the latest stable Unraid, 7.0.1 and Plex was the only one to give me the error when I tried to use the webUI from the Docker tab.