Why does internet disconnect with Keenetic Hopper DSL and Mercusys MR50G in AP mode (connection loops)?

I have set up a network with a Keenetic Hopper DSL downstairs and a Mercusys MR50G upstairs. However, when I switch the Mercusys MR50G to AP mode, only the devices connected to the MR50G (via wired or wireless) experience intermittent internet disconnections. The connection drops for about 10 seconds and then reconnects that loops. Solutions I've Tried: Switched MR50G to AP mode and connected directly. Result: Devices connected to the MR50G still experience intermittent internet disconnections. Assigned static IPs to MR50G within and outside the DHCP range. Result: The issue persisted, and the

Question by Burak Sümer on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.