Why'd they stop too early?

Currently I am using the sonatina soundfonts. I'd imagine my problem would apply to any sfz file used as a soundfont used on musescore.
The issue that I face is that the playback sound cuts off too early. For instance, at measure 18 I have the strings and some other instruments hold a dotted whole note, while the timpani builds in strength. Even tied notes will cut off before four beats in a measure, regardless of tempo.
Please help! This wasn't happening when I first started using the soundfonts!