A lot of people have been complaining on the reviews that when they upgrade their equipment the stats keep going down. This article explains why:
Items except baits can be upgraded by using scrolls or gold.(You can ask your friends or purchase scrolls with stars.) Up to Level 3, upgrade success rate is 100% so make sure to upgrade and check your items. From level 4, you may fail at upgrading. From Level 7. upgrade level may drop so be careful. Upgrading can be achieved up to level 15
This system was put into place by the game developer's to limit the convenience and simplicity of maxing out your player stats. If there were no fail and there were always a 100% success rate on upgrading then everyone would be SUPERANGLER and the game would be too easy.
Levels 1- 3 -->100% Upgrade Success Rate
Levels 4-7 -->May fail at upgrading so upgrading is a gamble
Levels 7-15 --> Will probably fail (but may not) so do not try unless you have 10 stars to repair equip