Yes see what happens with TS and QoS disabled and the end points reconfigured and your new wireless mode settings. Your on a ISP with a uplink thats over 2Mb. There is a softcap on some older generation routers that only use 2Mb. This maybe an issue here. Maybe.
Test these new settings and see if the router still fails, if so, go for the FW update. Use the update process please.