Clicks after loopback

Having trouble with LMMS? Ask about it here.
Hello

I'm using Audio File Processor with a small sound (322ms) that I want to loop at the end. With ping-pong loop enabled every time the playhead returns to a loopback point I hear a click. Increasing envelope attack or release doesn't help because this click appears "inside" the note. Any suggestions?

I'd like to attach a project file but how do I transfer used audio with it? Putting it the archive maybe?

Edit: small grammatical fixes
SOLVED:
Exported projects don't have clicks, probably there are problems with my audio system