I have had this bad experience with them. I had a checked allowance of 25kgs but had a lot less. Then after I checked by bag and going through to security they stopped and made me weigh my hand luggage and they refused to let me go because I had 1 kg extra. This was security for Air Asia and not the airport one. The airport one was just after that. They wanted me to leave something behind. After a lot of haggling back at the check in counter and in fact calling their management, I was able to retrieve my bag and put some stuff into my bag and bring down the carry on weight to 7 kgs.
Now I first check my carry on and get them to put on a tag on it even before I put my suitcase on the scale.