Reflection probes trigger an update every time you cross a parcel connected even when both parcels are using the same EEP setting and same large probe, that is disrupting, it should not trigger an update if both parcels are using the same EEP within the same region, same owner. It's very common in regions like Bay City, Nautilus (not limited to it... ), where we cannot merge parcels, that was not problem before PBR, and reflection probes are quite slow to update ( 1 to 3 seconds ) noticeably "brightening" the scene while its updating. In my case I have several in Bay City, and 3 scenes share two or more parcels connected.

Left an example here: http://maps.secondlife.com/secondlife/Bay%20City%20-%20Moloch/162/227/26

2 parcels, same owner, same region, same EEP... 1 probe, 1 scene... can be observed by walking the concrete walkway.

That only happens with "Use Shared Environment", does not happen if you select Midday (the new one) on the viewer as a fixed environment.