when it happens, log in and get a screensnip of the cable connections page and event logs. That shows us the connection back to the ISP

As you mentioned, you are experiencing with slow speed internet connection on SB8200, could you let us know whether the modem connected with any router or connected directly to the computer through hardwired.

Since you are experiencing with slow speed, I suggest you to check the cable signals to make sure all the signals are in range.

To check the cable signals, find the link given below:

http://arris.force.com/consumers/articles/General_FAQs/SB8200-Cable-Signal-Levels

My speed just went from 700mb to 10 mb.  Lights on the modem are all green.  Here is a snap shot of the modem:

As you mentioned the downstream bonded channel’s power level and SNR level are in range.

I suggested you to share the upstream channel’s signal levels to make sure all the signals are in range.

You have a ton of uncorrectables (errors). 

Check your line for loose connections, old/bad/cheap connections, kinked wires, etc. 

Try  moving the modem to right where the coax comes into the home and direct connect it there. That rules out anything within the walls causing issues. 

If none of that helps, the ISP needs to check the line