I thought I had lost remote access to a 2820. I can ping the IP without issue, but when I tried to telnet to it, I just got a blank screen. I could type on the screen but it appeared that nothing was happening. I noticed that if I hit the 7 key, Putty would close. This was telling me that I was getting to the 2820 but it was not echoing back the screen info for me to see. I tried again but with the options to reboot the SCU (1,2,8,y) ...it worked. The next time I logged in, I was getting the screen to populate like it should. What could be the cause of this. It will work correctly for 5 minutes sometimes and 30 days other times. I don't mind doing this workaround, but there is a large repair team behind me that I don't want to just be typing in stuff that could cause an issue.
It could be a bug, or possibly a flow-control setting. What firmware is it running, and have you looked at release notes for more recent firmware? Also try different flow control settings.
When it becomes unresponsive, does sending Ctrl-Q bring it back? If so, disable software flow control on the device.