Notes cut out half way

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Sometimes when I'm placing notes down in the piano roll (blue notes) I will adjust the note so that it is say half a bar long but the sound will only last for half of the note. So for the first half of the note the sound plays and then the second half is silence. I've tried everything and don't know what to do. Help would be much appreciated, thanks.
Welcome to LMMS.
What instrument is it?
Some instruments don't sustain a long note duration, you may want to try another instrument in it's place.
I thought that initially but I have used the same instrument (one of the bass sounds) for its full length, which is half a bar, at the start of the song but than else where it cuts out at only a quarter of a bar
I restarted it and it seems to be working fine now. Thanks any ways.
have to ask you what lmms you use, and on which OS
The 'half-length-sound' was a bug in an early pre-release, if you have that, for some reason, you should upgrade
Current stable version is 1.1.3
https://lmms.io/download/#windows