Sounds like you are getting rf interference on the MRF250. There is an easy way to check for this there are two lights on the top of the MRF250. One is for power the other is status. The power light should always be lit up. The status light should only light up when buttons are hit on the remote control. If it's red or blinking slightly (cup your hand over it to check to see if it's slightly blinking) and your not hitting anything on the remote you have interference.

There are three ways you can try and resolve this; one, try moving the entire base station around a little until the light stops blinking. Two, switch to a different rf channel on the base station. Also make sure it's not set to zero.

I would also recommend assigning the IR ports in the programming software & make sure they are not set to all. I would also leave it off of blast mode, using this is a bad idea. It's also very important the emitter is on the right spot on the the DirecTV box. To check this have one person move the emitter around while another person repeatedly hits the channel up button on the remote.

Sorry to be the bearer of bad news, but the MRF250 is known for having major rf issues. I pulled and replaced every single one I ever sold with an MRF-350.