Check your hotends when buying a new wanhao i3 or maker select. I had my maker select for about year and anything above low speed it would print poorly. Finally fed up I disassembled the hot end and aluminum shavings fell out of the heater block! To save pennies they aren’t washing the parts after cutting them. So during assembly shavings can fall into the chamber.
I used a fine copper wire to push out the plug in the nozzle and then cut it in half. I found an aluminum shaving inside. Ugh!
So my recommendation now is not only check the frame screws when buying one of these printers but also disassemble the hot end and check.