Common causes, roughly in order of likelihood: channel congestion from neighbouring apartment WiFi networks (fix: set a fixed 2.4GHz channel like 1, 6 or 11 instead of auto); two routers on the same network fighting each other (a genuinely common apartment issue we see often); outdated router firmware; or an actual ISP line fault (test by connecting via Ethernet — if it still drops out wired, it's not a WiFi problem).

常见原因大致按概率排序：邻居公寓WiFi太多导致频道拥挤(解决办法：把2.4GHz频道手动固定到1、6或11，而不是用自动)；家里两个路由器在同一网络互相打架(公寓里真的很常见)；路由器固件太旧；或者是ISP线路本身的故障(用网线连接测试，如果有线也掉线，那就不是WiFi的问题)。