This maybe isn’t your issue, but might help if you’re using a cheap MIDI to USB link
I have had a problem with MIDI notes hanging recently. I blamed it on using an old Korg N5 keyboard as a temporary mother keyboard. Then today I switched to an audio interface (Behringer FCA610) which includes MIDI and all my problems disappeared.
My conclusion is that the cheap MIDI to USB link from Ebay that I was using is the problem. This one has a small plastic bubble with a couple of lights on it, two MIDIS in/out and a USB connection. The problem is that most of the time it works fine, then I get note off problems for a while seemingly at random. My message is, don’t be tempted by these cheap solutions. This one simply doesn’t work correctly all the time.
P