I would stay as far away from the D* people at Costco as I could, unless it was to test to see how little they know. The clients just suck and they make anything else they're connected to potentially suck too. What you're describing is exactly what happened after a few months with my client. Both times I have used it, 3 different client devices. I loved it at first because it brought my out of market locals from the AM21 into my bedroom without a separate AM21 and OTA run. Then, it just started to @#%! the bed. I got a new one. Same thing. I got another new one when I moved. Same thing. I would recommend contacting D* and basically tell them that you're a new customer and it's just not working and your former provider's equipment worked and they are sending enticing "come back" deals. Maybe you can sweet talk someone into swapping the client for a HR24. Forget the 4K until there's something that can deal with it without a client. Currently, I have a HDMI splitter and just share 1 receiver on 2 TVs.
I have said it before, but I don't know if you've seen it. I have referred 4 people to Directv. 3 of them left before the 2 year contract because of the clients and I look like an idiot to all of them. The 4th person has 2 HR24's and I told her to hold onto those as long as you possibly can. If one dies, get a Genie, but keep the working HR24. I won't refer anyone again until this is not the system they use.