2 Routers connected to each other:

One running hotspot
One running UM

The UM RB can only show up to 49 active users.
As soon as more users log-in on hotspot RB, its log gets filled with "Radius accounting request not sent no response". and the UM RB never increases number of logged-in users beyond "49".

and when logged-in users drop below 50 on hotspot RB, the radius error stops.

I changed ROS to 5.12 - 5.14 and 4.17 all the same??????

Because you only have a Level 5 License - http://wiki.mikrotik.com/wiki/Manual:License

OMG... I searched the entire web but not in license section..

Now its clear how license are sensitive when its triggered.

well, I don't know if all RB433ah produced with default level 5 license. I don't know if I should bother to look through the rest of my other RB433ah since I have few laying around.. some was bought previously and some just bought recently.

if so, maybe instead of purchasing level 6 license, I should just buy a faster RB with default level 6 license.

Thank you jtroybailey and please accept my Karma.