I'd suspect your hub before I'd question the stick. Hence why I said "hardware" not "miner". What's your setup?
I'm running the stick on my "normal" rig since I also run my e-mail server out of it and let it mine when I'm afk. The stick was initially positioned in both USB 2.0 and USB 3.0 ports, but performed in about the same way. Since yesterday I moved it to a powered UH700 USB hub (max 5 A total, max 1.5 A per port). The stick is the only thing connected to the hub. This resulted in the GH/s being the same, but the stick not slowing down to a crawl over time.
As for the power supply, the hub is having an external power cable and is said to deliver 1.5 A on 3 charging ports. Additionally, it is the only thing plugged into the USB port at this moment.
This isn´t enough for higher frequencies. What is your voltage setting? The potentiometer at the right bottom corner on the backside has a flat side. Turn it to about 3 o´clock. Maybe 2 or 1 o`clock and see if the hashrate is getting stable. Use a frequency setting of 50 MHz for the tests. If it´s a power issue you sould at least get it running with this settings and a current of 1.5 A.
My UH700 gives me 5 A at most with normal output on 4 ports and 1.5 A per charging port on 3 specific "charging ports". I thought the stick was supposed to work on that current.
And it has ben stable averaging around 3,4 GH/s for the last 12 hours. Do you still suggest that I should turn the potentiometer to 3 o'clock? And as a back-up check, what should it be at for 150 MHz and 1.5 A (or won't I be able to run it at that?