To me that's a sign of a resource hungry app.
Apparently, after it caches it a few times (a little more each time it plays) it runs smoothly.
Prior, it may be exhausting your system and simply dropping things to keep up.

'Resource hungry' is a relative thing.
If an app needs X amount of free RAM to run, and you offer it W (less), then it may make sacrifices to keep up.
That's my first inclination to look at. What are system specs for that computer?

/The RAM example above could also be caused by CPU, drive speed, network activity and a bunch of other things that could make this issue occur. Hard to say without deeper investigation/

I do not work here, but the benefits are still awesome
Make your sound your own!