midi data distortion

I have a Technics PR-700, a great digital piano, but about 12 years old. I connect it to FL using a midi cable. The midi data comes in fine and sounds great, but sometimes, for no apparent reason, some notes are cut or mis-timed. I don't think it's FL because it does the same on other midi software. It might have to do with the sustain pedal because it seems it occurs more/only when I use it. The note data coming in are sometimes not sustained or cut all together. It's not my pedal technic, because when I play regularly through the piano speakers, it sounds fine. I even recorded me playing where the midi data was fine, and sent that through, but when FL receives it, it distorts it in random places. I don't think it's the cable because I tried other ones. I just discovered Midiox but haven't tried it yet. Would this program be able to tell me if it's my piano? If so, how would I use it to tell me this. I've been trying to figure out this problem for a long time now and tweaked every known setting, but still doesn't help. If anybody have any clues, please let me know.