USB Oscilloscope DSO-U2400 400MS/s

After couple of months it happened first defect: sensitivity of the channel 1 is NOT regulated. I tried to contact Customer Service but without success. And I used the device "AS IS". But after 5 months it appeared second and fatal trouble: the screen shows ugly traces on both channels IN SPITE OF the probes are DISCONNECTED. Device is useless. How can I obtain the device in normal condition instead of this junk?

The unit installed cleanly and has been a pleasure to use. One thing missing from the description is the accessories -- it comes with two probes. The variety of measurements it can do is impressive, even with a usable FFT. The trigger is adequate, though slightly low gain compared to most scopes. The aluminum case is excellent, though a grounding post would be a nice addition. There is no external trigger input, nor any way to sync one unit to others, though the manual says you can run up to 4 units, giving 8 channels total on the same screen. The screen resizes to 4 settings. Power consumption seems fairly low. The main limits are the sampling speed (400M), the 40vpp limit on the input, and the 8 bits resolution which causes quantizing noise to appear as an annoying low level buzz, but in general I'm impressed. I don't think you can do better for $200. This is so much better than my Hantek 5200A.