Here are all important links:
http://lmms.io/forum/viewtopic.php?f=1&t=4740
-A few rules and useful forum instructions
If you like to introduce yourself, to the community, go here:
http://lmms.io/forum/viewtopic.php?f=4&t=4480
That happens if the last note is a fraction too long. in piano-roll, Use the highest magnification and the highest Q-value (1/192) Then shorten your last note in the block until it is inside the last bar that you intend to play.
Afair its also one of the things i show in Rookie-guide
https://www.youtube.com/watch?v=hcUCFfQ3wn8