If you are ever doing anything like `load("res://EnemyScene.tscn")` where you are loading a sound effect, scene, or script at runtime -- that might cause it. I'd try to cut down on runtime loading of stuff, and `preload` where possible, or spawn nodes when your game starts and then switch them visible/invisible.
Unfortunately I'm not 100% sure what causes these issues -- for me, it just seems to occur during scene transitions or when a lot of things are loaded. I'm sorry.
Guys, did you try enabling multithreaded html5 export? By default, it one thread, it may be that audio cant refill buffer when game does large delay spikes (loading a big chunk of something).
I didn't tried this yet, my games usually one scenes. But I'm interested in resolving this issue.
Be notified: multithreaded html5 build can work on smaller set of modern browsers, please check docs.
