How do you use the arpeggiator in Sonar 8.5.3 PE?

The arp timing drifts in live play mode. Am I doing something wrong or am I trying to use it in a way that it's not intended?
 
Here's what I am doing.
 
Open new project. Keep project tempo at default 120bpm. Load Dim Pro instance, patch: "piano & bells." cue arp -keyboard riffs -21. Load Session Drummer 3 -program: Misfitkit.
 
arm: Dim Pro. press record. start midi pattern "B" in loop mode in Session Drummer. Play Dim Pro. What happens is this: maybe 45 seconds or so into live play the timings in the arp and session drummer begin to separate. It is possible my timing is a nano-tick off but my timing as a player is quite on. It could very well be my timing is the issue.
 
How can a live player effectively use this arp? Is it intended for step sequence data entry only? How do you use it? or, must I bust some serious hours into metronome mode? In other words; I am screwing up?
 
The answer is probably so damned obvious. So go ahead, beat me up. I'll gladly take it. Thanks.   Leonard
 
ps.. If you actually load that up and work it? ..it'll probably put a smile on your face.

I'm now able to "play" the arp just like you'd expect you could. A full 5 minutes interaction with Cake's metronome went without time drift from anywhere. Awesome! 

 I had this "issue" in PE 8.5.2. Having just now upgraded I mistakenly thought this problem persisted. It's working now!

 There's some serious chops buried in that arp! All right. It's back to work, now. Have fun, everyone. Thanks. Leonard
  

I'm pretty sure this was a glitch issue resolved with the latest version 8.5.3 install. Thanks again, I appreciate this. Leonard

Good that you're flowing now.  But it does pay to keep in mind the affect the loop "points" have, and the snap-to-grid has in any case.

Enjoy.

I've just played 5 minutes through without drift with Snap To Grid off, freeform with input quantize disabled. I'm pretty sure this was a glitch issue resolved with the latest version 8.5.3 install.

 
I don't know. I think you might have been right the first time. In this scenario, Arp does seem to have some issues with live triggering.
 
I set it up the way you described, but driving a hardware synth. I've never really tried to play live with Arp engaged (and haven't used it that much in general), but I immediately ran into a lot of weird triggering and stuck stuck notes when sending note-off while Arp notes were playing. I suppose that latter effect is just the way Arp works, but it certainly has some strange side-effects.
 
But here's where things really went bad: When I played a simple alternating, minor third note pattern on measure boundaries, it sometimes sounded okay, and other times triggered at a strange point in the pattern, and seemed badly out of sync. When I looked at the recorded data, even hits that were only 2 ticks (1ms at 125BPM) late sounded horribly out of sync on playback. Then I bounced the clip so the Arp pattern was rendered to MIDI, and it played perfectly.
 
So I went back to the original clip, quantized it to 100% (both start times and durations), and it played perfectly. Then I tried sliding it later by up to 30 ticks to see if there was some threshold point where it would get whacky, but it still played in sync, just a little late. And finally, I went back to the original clip, which I had started playing at measure three, used Process > Slide to slide it back to the first measure without changeing the note offsets from the grid, and it played back perfectly. Undo the slide, and it plays like crap again with the same timings in a different measure.
 
I'd have to experiment some more, but there's definitely something a little screwy going on.
 
Incidentally, input quantize and snap grid should have no bearing on live input; they both operate only after the events are recorded.

When I looked at the recorded data, even hits that were only 2 ticks (1ms at 125BPM) late sounded horribly out of sync on playback.

 
For confirmation, I recorded the hardware synth playing the Arp pattern. My audio latency compensation is sample-accurate, and the MIDI transmission and synth response delay is on the order of 5-7 ticks, but the recorded pattern is about 125 ticks late throughout.
 
If I slide the MIDI clip back to the first measure as described in my previous post, the recorded transients fall right where they should.
 
Arp definitely has issues, and not just with live input.