Router disconnecting constantly after last firm update and also Inconsistent Download Speeds

Hi,

I recently updated my router to the latest firmware and started experiencing the following issues:

1) 4-5 Disconnections from router per day.  So I loose access to network drives and internet

2) Inconsistent internet download speeds.  Sometimes it will be 260 MBps but other times is 120 Mbps and sometimes 50 Mbps. 

3) The Media Server not working

Can anyone tell me how to revert back to a previous version or can someone from Tech support advise what to do?  I almost called the cable company until I realized it was the router.

Router: R7200 Updated version: V1.2.0.76_1.0.1