I just got the TCL 43S425 their newest 43 inch 4k TV on Oct 27th. I hooked it up to my HTPC and it has a really good picture, great response time, good color and brightness with minimal tweaking. Unfortunately it has a serious problem. After a few days (and really maybe 4-6 hours total use) it has started to get an error message 'Not enough power for USB device, consider connecting the power adapter if available' that takes up the bottom third of the screen, and returns immediately if dismissed. I have no USB device hooked up to it. In fact it gives this error message even when hooked to nothing at all. Then my HTPC started to get BSODs, but only when hooked up to the TV. Disconnect the TV and I can stress test the PC all I want with no errors, plug the TV in and I get a BSOD in a few minutes. I've tested this thoroughly, it is the TV causing the BSODs.
I've worked with TCL's support and they were all but useless. Their entire troubleshooting steps consisted of various versions of 'turn it off and on again' over several days and hours on the phone. The good news is that they are paying for shipping to return the TV and have it repaired in house, bad news is they do not cross ship because they say that they will repair my TV and return the same one.