I had the same problem after L2.70. I tried all of the suggested fixes to no avail. I called Dish Tech Support and got someone who didn't know what PIP was. After she was able to find a description of it in a manual she had me try the stuff I had already done. She then took my receiver info and filled out a report to forward to the next level of Tech Support. Several hours later my PIP was working fine. I don't know it they did something via remote, but I hadn't made any changes. I never got a call from Tech Support. My PIP is working fine now....
You'd be much better off to go buy a bird just so you can line the bottom of its cage with 'the manual'.
Since software updates change the operating characteristics of your receiver unpredictably, it would be pointless to even try to refer to it. The only good information in the manual is how to change the remote address and even then, it doesn't list all of the 'hidden, top secret' ones.
Most of us learn by trial and error as I did with your problem. It took about 6 button presses to figure out the solution because I hadn't used PIP since the update.