Message - XHR Timeout on certain functions. Maybe this is posted in a nother thread but I'm posting this again anyway. Simply because it was so annoying I dont want others to not be able to fix it quickly.
User stated: I fixed it disabling the uHTTPd Connection Reuse.
You can find it in Luci under
> Services > uHTTPd > Advanced Settings > Connection reuse = 0
or through SSH
> nano /etc/config/uhttpd > option http_keepalive '0'
Maybe consider setting default to 0 in other images? Unless theres a good reason to keep it at 20