Are you using ethernet or wifi backhaul? If wifi, switch to ethernet backhaul and try again.

Past reliability of wifi doesn't guarantee future results. Wifi is awful. Mesh systems that use wifi for backhual don't work great. Because wifi is awful. See my comment here.

Is this just something that could happen to older routers and maybe a component is failing or is there something I am missing that could fix this?

Sure. Those things are technically possible. But it's unlikely. More likely RF interference is causing your nodes to disconnect, assuming you are using wifi for backhual.