I've had the Echo for almost a year. It (she) controls my Hue lights. One of the group names for the lights is "the bedroom lights". Around a month ago, Alexa stopped understanding the group name. She gave the usual can't find group name in user profile or the other standard phrase she spits out. I've unplugged, reset, and have contacted customers service (3x) There are other things she's decided to not understand, like turning off the alarm in the morning. The last customer service rep had me change the group name to "the bed lights". It works. But it sounds dumb. I've gone with the British "the chamber lights". She understands bedroom fan, bedroom lights, but has decided to no longer understand bedroom lights. Nor to hear "Alexa stop" to turn off the alarm in the morning. She now also has trouble distinguishing between 15 and 50. Big difference when setting an alarm. And she willy nilly chooses when to hear her wake word. I'm sure there are other things, but she's in a time-out right now, being replaced by Siri for awhile. This is the same selective hearing I use at work, so I think this may be personal. Bottom line, she can't "hear" like she used to. Customer service did say this was a "thing" and put my name on a list. Oh, and they'll never get back to me when this is fixed, because, rest assured, I'm on the list.
She now no longer understands "The Living Room Lights" group. I have had that one for a year as well. Also, when you tell her to shut the f*ck up, when she repeats it back (as she doesn't understand the command) she censors the the word f*ck. So she can censor certain words but not hear other words. Luckily, I'm on the list.