DIAGNOSIS This is usually a Bluetooth audio compression artifact from a weak or congested signal, not a hardware speaker fault.
FIX Move your phone/device closer to the speaker (within 3 feet), turn off Wi-Fi on the device to reduce RF interference, and ensure no physical obstructions are between them.
IF THAT DIDN'T WORK Disconnect and re-pair the Bluetooth connection. If it persists on multiple sources, perform a factory reset (power on, then hold Volume Up + Volume Down for 10 seconds).
HEADS UP The Charge 5 uses a single racetrack driver. Distortion at max volume is normal for complex bass tracks; back off a couple of clicks from maximum.