Currently, I understand there are specific limitations as to the spillover behavior functionality.
1) Rig level setting [Rig Spillover Off], which by default, my Stage shows unchecked for all rigs in my Performance
2) Delays/Verbs (where applicable) must have Mix set as "Pre" vs "Post"
2) Delays/Reverbs must be in the DLY / REV slots respectively, or the spillover feature will not function properly
(This would be a new request to research options to re-factor these rules to allow spillover on FX even if they are not in the dedicated slots)
Even when I build a given performance out following the above protocol/rules, I also think there are bugs (memory leaks perhaps?), because sometimes i get spillover that behaves correctly, but then other times it does not (I'm testing by playing short phrases and listening to the DLY/REV trails, and toggling between footswitches in the same performance, and sometimes the trails carry, other times the signal is just directly cut off. This is frustrating!