I used to have constant problems with my TiVo Stream, whether it was downloading or streaming, with "Unknown" errors or "Problems...", whether I was in my home WiFi or downloading away from home, and whether it was on an iPad or iPhone.
I ended up solving the problem. I bought an Airport Extreme 3rd gen. and shut down everything WiFi and network-related on my AT&T Uverse 2-wire gateway box. (I have only Uverse internet -- no land-line or TV service.) Now that the Airport Extreme is handling all the WiFi and hard-wired networking services, the TiVo Stream has become 99.9% reliable, both streaming and downloading in my WiFi and when downloading outside my WiFi.
My thought is that the TiVo ecosystem performs better with some routers than others. I spent hours and hours performing various voodoo on the AT&T router trying to ascertain if I had some obscure network setting that was causing unreliable behavior with my TiVo Stream. Resetting the AT&T box to stock settings didn't help, so I took a leap of faith and spent the buck$ on the Apple router. I got lucky -- my TiVo toys are all happy now.
I'm not saying the AT&T router is "incompatible" with our TiVo toys....but in my case, everything started working much better once I changed routers. If you've exhausted everything else you can think of, you might try changing routers.
Just my 2 cents!
2011: First Tivo Premiere (Ethernet)
2012: Second Tivo Premiere (Ethernet)
2012 Tivo Stream
2011 Slingbox Solo
Series 2 Humax DRT800 (Still in use for VHS->DVD)
Series 1 Philips (Retired)