Hi hendradianto Thank you for your asking. Kindly refer to the tips below for troubleshooting. 1. What is your current firmware? Setting >System>About Phone>Software information>Build Number Does the issue happen after any system/app update? 2. Please try "Network settings reset" Settings>System>Reset options>Reset Wi-Fi, mobile & Bluetooth 3. Try to enter "Safe Mode" to test your mobile internet, to check on the disturbance from the installed 3rd party Apps #How to enter and exit "Safe Mode" https://www.asus.com/support/FAQ/1005163/ 4. Check on your "Preferred network type" Settings>Connecttions>Mobile network 5. Have you tried to open/close Volte? Setting>Connecttions>Mobile network>Advanced>Disable Enhanced 4G LTE Mode
I also faced the same problem with my Zenfone 3 ZE520KL.
#1. OPR1.170623.026.WW_Phone-15.0410.1807.75 It happen just out the sudden. #2. Done. Still the same. #3. I've reset to factory setting and still the problem persist. #4. Done. Still the same. #5. Could not locate the advance setting as given. I've installed accubattery apps and it reported 1200mA-15000mA were drained when mobile data were enabled which probably the effect of the heating up.
I have been using this phone since 2016 and all this while has been great till now.