Pan pots disappearing on mono channels when routing to group

I’m not sure why this has started happening, but since updating to 8.5.1, whenever I route some mono vocal tracks to a group channel now, the pan pots for the individual tracks disappear & the tracks’ pan pots get centered. It doesn’t happen on stereo tracks, just mono. For backing vocals, my tracks are panned left & right, but they all flip to mono when routed to a group. It’s bizarre. Any ideas? I’ve contacted support, but haven’t heard anything back.