We have a tr-rack and are generally very pleased with it, However recently we have been having a bit of trouble with sticking notes, if anyone can help that would be great

Depending on your sequencer's MIDI echo settings and/or your MIDI interface, there could be a number of reasons for the stuck notes. Try assigning all of your synths and/or modules their own MIDI channels, and make sure your MIDI echo is disabled on the channel you assign to the TR-Rack. If this fails, you could just hit the reset button on the TR Rack and that should stop a stuck note.