Yet DTV continues to ship these older model as replacements or addition units. My HR22-100 has gotten slower over the last month as well. I was surprised when I received an older receiver. Seems these older refurbed models are not worth the headaches to customers or techs.
When that happens, you simply must fight it. Argue enough, politely and persistently, and you will win. I always have. If you don't get satisfaction from a CSR, escalate. There are several levels that you can reach, the topmost being the Case Management Group. If you argue enough you WILL be sent to Case Management and you WILL be satisfied.
Above all, hold your temper in check, be patient and polite and you will be rewarded. Since the advent of the 24s and their stabilization I have never failed to get a 24 for a replacement. And, it seems that they actually do refurbish the 24s, something that I never saw any evidence of with the 21 Series DVRs.