Program A arp not relatching when notes are being playing on Program B

[notionsdepartment]

When playing a Split A/B patch, I'm running into a problem where Program A, when set to ARP=ON and ARP RELATCH=ON, is not relatching if I'm playing notes in Program B at the same time. It's very odd, because as far as I knew the two programs were completely independent. But it's really messing up some of my arrangements. Can anyone else confirm this behavior on their machines?

Thanks!