I have 3 deco m4 plus router fritz box 7560. Fritz box is main router and deco is only AP. Im losing wifi in my handy Xiaomi mi 9t pro  10+ times a day. My handy show wifi  full signal but no internet conection. only helps off and on wifi in my handy. all my deco ist connected to swith with cabel and the swith is connected to fritz box. What can i do to resolved this problem.