From this topic on the forums:
When playing sources using Source:clone() and Source:play(), love2d bugs out and will not play a “stream” source more than once even after restarting the program. A full restart of the computer is required to get the source to play only once before the same issue happens all over again. After removing the Source:clone(), the source played normally (although the source can’t be stacked now).
Issue does not apply to static sources. This issue may apply to other versions, I have not tested whether it does.
Will add some code if I can find the time to replicate the bug in a separate more simplified program.
(Current solution was to stop using Source:clone() in the project).