Other things that can make the tube overheat is to let the exhaust fan grid get clogged. That makes the fan run less efficiently and the hot air isn’t exhausted out of the machine. You might see smoke building up in the bed and will get a lot of ashy buildup deposited on the tube and lenses, requiring more frequent cleaning.
Check your intake (right side under the machine…make sure it’s not blocked and has good air flow.) If you can improve air flow into the machine by moving the unit away from a wall, do that too.
Then remove the exhaust hose at the machine and look at the grid plate covering the back exhaust fan. If it’s clogged up, clean it with a vacuum hose and brush.
Check the hose to make sure it’s not obstructed and is blowing air at the outlet as well. Make sure there are no tight bends or loops in the hose.
If you are still having trouble getting complete cut through in one pass, just send a second cut without moving either the materials on the bed or the image on the screen. It will cut in exactly the same place and finish the cut so you don’t waste material. You can use a doubled up piece of Gorilla Tape to test the cuts by lifting them out. To avoid having to do that as often, use Honeycomb Pins to pin the material down very flat.