I haven't had the problems that people are talking about. I have had a bad sensor wire which caused me to not Finnish the A main, replaced the wire and was all good again.
I run 3 flow works. 1 in mod, 2 in stock. Had one in my 1/10 dex 410 also but you must have a fan on it for that. These things run very smooth and I've been very happy with them. I also have a couple Tekin rx8 and 2 rs. I switched out the tekin rs for these because I can gear up a tooth on the motor without a loss in performance and it just feels like it has more power without getting hot.
The answer for why people are selling is because there are new esc's out there and a lot of people like trying new stuff, usually because it's what everyone at their local track is talking about and running.
I hope you can figure out the problems. Let us know what it turns out to be. Try rebinding your receiver also. Once you do that set your setting in the radio for 100 percent and recalibrate the esc again. Just one more thing to try before getting rid of it and or sending it in. I never go to 150 percent, although it's supposed to make the range of throttle even smoother.