fix: prevent from shifting channel position (#908)

hxd/snd/Manager.hx

@@ -361,7 +361,7 @@ class Manager {
 				#end
 				playedSamples = 0;
 			}
-			c.position = (s.start + playedSamples) / s.buffers[0].sampleRate;
+			c.position = playedSamples / s.buffers[0].sampleRate;
 			c.positionChanged = false;
 
 			// enqueue next buffers
@@ -816,4 +816,4 @@ class Manager {
 			if( snd != null && snd.channel == c ) snd.channel = null;
 		}
 	}
-}
+}