Adamo Official … this as a common issue that happens to all controllers at some point. the reason is either the internal housings bands that keep the stick straight are broken or stretched, or that there is dust or debris preventing the stick from returning to its neutral state. you can follow this guide to disassemble the device and attempt to clean the housing with isopropyl alcohol:
ASUS TV500BG Bluetooth Controller Disassembly
if cleaning doesnt fix the issue, or you see the bands are stretched or damaged, you can replace the controller housing. this will require tools and experience. the parts for this particular controller isnt advertised, but this is a standard part for controllers of this type. here is a link for a potential match ( youll want to verify pins and shape while you have the device open) , but you can see that this part is for playstation, xbox and possibly yours as well:
if this doesnt match the profile of yours, just google joystick replacement parts and find a match.
post back with any other questions if needed.