On a slightly related matter, what I observed was the the UIW series of STBs are a little less sensitive to IR as well. I have had a harmony hub for quite a while and I went through three or four different receivers including the Arris VIP 5662W in the exact same spot. Harmony never missed a beat(or I should say the receivers never missed a command). However, recently I got the UIW 8001 in place of VIP 5662 and ever since, it misses several commands. I have to press again and some time up to 4 times.
Tried to orient both the receiver and hub in various directions and so far it hasn't helped.
Initially, I thought it was my remote and bought a better one(ultimate home) and paired to the hub. No change. Next step is going to be putting a dedicated IR blaster. Just thought I let people know.