When I have encountered this in the past I have highlighted every track containing data, whether MIDI or Audio; if it had an event it gets highlighted.
Then I set the From to the point I want it to stop playing, and the Thru to something ridiculous like 2000-1-0
Then use Cut, making sure the Close Gap checkbox is enabled.
Then Save and reopen.

It's a pain but it seemed to get rid of any weird extraneous data that caused it.
Another thing that *could cause this is if a MIDI event never got the Note Off signal .. it could want to go on forever even if the sample stopped sounding ..

There may be a way using Sysex to force a stop from whatever triggering device you are using. I've never delved that far into it as the above solution usually worked for me.
It has worked on a couple systems I know of, no idea why or any explanation.

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