Hi friends
Thank you for your asking. I just checked my ZB602KL, attaching firmware version WW-16.2017.2007.084 and WW-17.2017.2006.429, and both device work properly with the earphones plug in/out. The voice performance and the icon also did not encounter the same situation as yours.
Please backup the data and try "the Factory Reset" first.
Settings>System>Advanced>Reset options>Erase all data(factory reset)
Try to clean the port with the compressed air can, too.
If the situation remains the same, according to what you described, please contact ASUS repair center in the country of your residence:
https://www.asus.com/support/Service-Center-All-Countries/If it is impossible to access the service center during Covid-19 period, please try Call us:
https://www.asus.com/support/CallUs