Speed ​​ok, unfortunately heat problems

I have this thing for over a year. At first everything went as desired. After about 2 months, the first problems began. Sporadic connection aborts. The thing restarts and then you go after 2 minutes on .... until the next crash. I now really only as a last resort to run the new modem arrives ... currently I can of +20 in 24 crashes reported .... neatly recorded by the PFSense sitting behind. Thankfully just winter ... if I abstöpsle the modem and let evaporate on the terrace 10 minutes, then it runs the next 2 hours stable.