Anytime you launch an attack on an Emporium while city raids are in progress the Emporium raid symbol appears in front of - or replaces - the city raid symbol even if the city raids have lower timer. All the bubbles in the bar start flashing while the Emporium attack is in progress. Clicking on the raid bubble no longer takes you to the raid summary screen. It does not depend on how many returning units there are.
For example if there 4 active bubbles: City/PP raid, city siege, spying, returning units and you launch an attack against an occupied Emporium, the city/PP raid symbol gets replaced by the siege symbol, all 4 bubbles start flashing/flickering and clicking on the raid bubble no longer takes you to the raid screen.
Let me try to get a screen shot when there are two siege bubbles
Before I launched an Emporium attack - 1 raid - 1 siege
https://gyazo.com/acd184c557b30ce248b9ddbd33a007a1
7 minutes later after I launched it... where did the City raid bubble go? why are there 2 siege bubbles? The screen is flashing and the bubbles no longer connect to the raid progress screen.
https://gyazo.com/e0992747c11cb51b1af879c515d9687e