Vern C
I'm not sure what changed between X3 and Platinum, but there ya go.

Me either, but any time I hear somebody has a MIDI problem like this - I'll tell them to look at that setting.
I'm the same - I never thought twice about this setting and always had it on the default of 250ms, and never had a problem. Changing it to 500 didn't help me but 999 did. So you're proving that it might even have to go higher ;-)
 
Maybe after all the "new version" traffic dies down, we can find out what's actually changed...

Well, having it at 1500 does present the issue of the first note of the loop being cut off at random times, but it's close enough to what I want and probably as close as I'm going to get right.
 
Remember: These midi issues are only present when I'm using a humanizer midi effect on the midi track. Cakewalk's Quantize plugin has a randomize feature and it gave the same result. You could maybe try to test it and see what result you get, if you want to. Just a suggestion.
 
With that said, something with the midi definitely changed between X3 and Platinum, as said earlier.

My problem was just playing back a normal drum part (in to Superior 2) that worked fine in X3.
I wasn't doing anything "fancy" at all - but when I loaded the song in to Platinum, it was dropping random notes.