The thing is, XPS laptop have issues going to S3 Sleep/Modern Standby. There are many threads about battery draining due to this.
The question is, why isn't the laptop shutting down properly when it begins to overheat inside a bag? In any case, this will probably not void the warranty in most countries.
The question is, why isn't the laptop shutting down properly when it begins to overheat inside a bag? In any case, this will probably not void the warranty in most countries.