Realtime Rate & Collecting data

Device: Linksys WRT3200ACM
FW: OpenWrt 19.07.7 r11306-c4a6851c72 / LuCI openwrt-19.07 branch git-21.107.58152-c19c716

I got a problem with displaying Realtime Rate data in Status > Realtime graph > Rate tab.
All other tabs showing data, however Rate tab in Download and Upload section constantly got Collecting data...

Anybody got this kind of issue?
Is there any package that need to be installed (additionally to standard packaged) to get this working?
I am interested to see current download and upload rate per IP.

If this was mentioned in forum, please point me into the right direction.