customer support a bit complicated
I got three adapters from K&F One does not lock the lens. I sent a mail to K&F, the asked me to send a video. I sent a video. They asked to make another one. i sent the video. And guess what? They asked me to sent a third video. I even analysed the problem for them by disassembling the adapter and said that it's getting urgent. No answer for two days. Update: They send out another one, problem solved.