This empirically is due to the binhex-preclear install but only indirectly. When you install that plugin it asks you for volume mounts to give to the underlying docker daemon for mounting inside the docker container. Host Path 6 is /boot/config/plugins/dynamix/dynamix.cfg. This *should* be a file, I'm assuming, but didn't exist on my unraid. When you give docker a path that doesn't exist it will automatically create a folder given that path. So when I installed binhex-preclear the docker daemon created the folder /boot/config/plugins/dynamix/dynamix.cfg/ If you make this folder and refresh your WebUI you will see that it generates php errors described above.
The *easiest* fix is:
1. Uninstall the binhex-preclear plugin/app
2. remove that path from your dynamix plugins folder (or at the very least move it to another name that *doesn't* end in .cfg)
* You can move the offending directory out of the way via the terminal with the command:
* mv /boot/config/plugins/dynamix/dynamix.cfg /boot/config/plugins/dynamix/dynamix.cfg.broken
* Or if you want to remove it
* rmdir /boot/config/plugins/dynamix/dynamix.cfg
3. Now refresh the WebUI and you'll see the errors are gone.
Now if you want to reinstall the binhex-preclear plugin you should first create that file that the plugin wants to pass through to the docker container. From the terminal run the command:
touch /boot/config/plugins/dynamix/dynamix.cfg
[EDIT] Squid pointed out that if you make changes within Settings -> Display Settings this will create the file /boot/config/plugins/dynamix/dynamix.cfg so there's no need to enter the terminal if you don't want to.
Then proceed with the install as you normally would and things should operate just fine.