I think this happens the first time the particles are instantiated. My game had that issue and the solution I found online was to just instantiate them at the beginning with a black screen on top and then queue_free'd them and it solved the issue, like a loading screen.
Viewing post in the Lord of Eternal Dream jam comments
Oh, that's what's going on, i see. Now I remember what in first start after upload I had some lags too, but thought this is connection issue, just refreshed the page and forget about it. Thank you very much for pointing that out!
Btw, maybe do you know where I can learn about audio? As you can hear the volume of the sounds changing and it`s not my will, i can`t find how to fix it.