How can I fix my treadmill, belt slips at high speeds?

Hello, I know this question has been brought up numerous times but I have a slightly different slipping issue. I can jog at about 6.5kph for about 20mins fine but if doing interval training, I go up to 9-10kph for 2 mins. Or I can jog for about 10 mins at 7.0kph after either scenario, once the treadmill heats up the belt slips. If I balance one hand on the handle, it won't slip at these speeds. The treadmill runs very quiet and makes no noises what so ever. After running at the high speeds, sometimes I can smell something hot, not quite burning but like you just plugged in a glue gun. I can't find my manual and this is a generic treadmill. I really like this treadmill as the motor is powerful and has lots of great programs. Thanks for any help. I love my treadmill and have lost nearly 70 pounds from jogging.