My Galaxy TabPro SM T520 works great unless it goes into standby. Then I have to hold the buttons to reboot it, but it doesn't always work right away. Does anyone know what could be causing this?

I don't know what would be causing it but I would either do a system reset and return the tablet to factory specs to start over or I would start uninstalling apps until it stopped freezing in standby mode. I think the system reset would be the best solution.