I have several varieties of the 3105g models around and it does appear heat is the issue for us. The hits get so hot, a hard reboot is required to regain control.
We installed ac powered mini fans to keep the devices cool and have not had the issue happen since.
Running 8.5.1 currently (just upgraded 2 weeks ago) and still going strong. I have been through all of the firmware releases and none have solved the issue. The fans, so far, have.