Bluetooth signal is transmitted wirelessly and signals can be affected, which results in intermittent sound of earbuds, in the following conditions:

The distance between the earbuds and your Bluetooth device is at the edge of the Bluetooth pairable distance.
Transmitted signals encounter obstacles or human body blockage.
There are high-power electronic devices nearby.
There are other Bluetooth devices and are being turned on/off nearby.
To resume stable connection between the earbuds and your Bluetooth device, try to avoid the above conditions and do the pairing again.

Why isn't the sound clear/consistent sometimes?
Connection is not stable.

Why is the left earbud charging time longer than the right earbud?
There could be differences in the using of the left and right usage, which results in inconsistent charging time. Besides, the left earbud is the main earbud. Some LED indicates and voice prompts are performed by the left earbud, which may also result in inconsistent charging time.

Package Contents :
Wireless earbuds : 1 pair (left and right)
Charging case : 1
Ear tips: 3 pairs (large, medium, small)
Charging cable: 1