Did you track down WHY you are getting stuck notes?
What are you using as a controller? Is there any sys-ex or controller data that is choking the transmission? Have you got any MIDI connector or cable problems?
Is there any common factor to the hung notes (playing a certain style or SMF or extensive use of a bender or foot pedal)? Do they only happen in one mode, or with a certain controller?
While it’s nice to know the All Notes Off command, probably best to track down the problem rather that put a bandage over it…
An arranger is just a tool. What matters is what you build with it..!