These sorts of issues can also be due to noisy power supplies. Cheap power supplies can have a ton of AC ripple which will cause all sorts of strange behavior. Also I have noticed the 3.3V output of some ESP8266 boards to vary enough that some work great without a logic shifter and some don’t. It is probably best to use the logic shifter and get the signal level to 5V which will greatly improve noise resistance on the data line. I have also noticed that many USB power adapters are extremely noisy as well.