Thank you for your asking. Kindly provide the information below so that we can better assist you.
1. Your current firmware version
Settings>System>About Phone>Build Number
If you try to update to the latest version WW-16.2017.2007.084, does the issue still persist?
#ZB602KL Firmware Spothttps://www.asus.com/supportonly/ZenFone%20Max%20Pro(M1)(ZB602KL)/HelpDesk_BIOS/
#Firmware Update Guidehttps://www.asus.com/support/faq/1009748
2. Does the issue persist in another cable earphones or bluetooth earphones? Do you use the original ASUS cable earphones?
3. Please try to enter "Safe Mode". If the function works well in Safe Mode yet the issue remains out of Safe Mode, please check on any disturbance from the installed 3rd party apps.
# How to enter and exit "Safe Mode"https://www.asus.com/support/FAQ/1005163/
4. Does the issue appear in playing music only, or does it happen in calling as well?
5. Also, please try "the Factory Reset"
Settings>System>Advanced>Reset options>Erase all data(factory reset)
Please note that once the Factory Reset is completed, all data, apps, settings and personal information will be deleted.