Imagine I launch a craft, and crash it on water. If I relaunch while the camera is underwater, the sound will be "muffled".
Relaunching again doesn't set it straight. It seems only 2 "methods" can return it to normal. One is restarting the game. The 2nd requires the craft to be launched again, crashing it on water again, but before relaunching, make sure the camera is above water.
Sound has been corrected ty.