Please tell us some basic information before asking for help:
Model Name: ASUS_X00TDE, Zenfone Max Pro M1
Firmware Version: PKQ1.WW_Phone-16.2017.2009.087-20200826
Rooted or not: Don't know
Frequency of Occurrence: 2 days ago, everything went well. Normal volume to the bluetooth headset. All of the sudden, the volume drops perhaps only 10% even turned to max.
APP Name & APP Version (If your issue relates to the app): Youtube, VLC, XPlayer, any APPS.
In addition to information above, please also provide as much details as you can, e.g., using scenario, what troubleshooting you've already done, screenshot, etc.
Have isolated the problem with bluetooth only as a wired headset gets the normal volume. The bluetooth headset also works well with another non-ASUS phone. Soft reboot doesn't solve the problem. Seen similar posts but not quite applicable.
Appreciate your help!