Stuck on Samsung screen, help needed

[rongkeys]

So my daughters tab 3 is stuck on the Samsung screen. Screen shows text : Samsung galaxy tab 3
I have tried a few searches and found a hard reset procedure, however as soon as it turns on it stays on this screen until the battery runs flat.

Things I have done.
Checked battery by removing and fitting to another tab3, it charges and works.

Tried hard reset as follows, refit battery terminal and back cover, hold volume down button, press power/lock button.
The tab screen flickers then the screen shows wording of Samsung Galaxy tab 3. I'm still holding the volume down button and can stay like that without any signs anything is happening.

I can post pics and vid if would help? Thanks

 

[rongkeys]

Unconnecting the battery is the only way to turn it off.
It has not had any software change- rooted?
Afaik it is up to date software.

 

[rongkeys]

Think it's a sm-210