I've flown a Phantom 3 Pro, Phantom 4, Mavic Air and Spark indoors. Really don't need GPS or sensors. Soft touch required on the sticks. Most important thing to remember is the drone will not stop if you let go of the sticks. You must put in opposite control input to slow and stop the drone.
Hummingbird.UAV that's good stuff! I subbed you on YT. It looks like your sensors were trying to compensate and going crazy! It's interesting looking at all the folks reactions to the drone. I think you've opened up a new market (pun intended) for drones. It was a very clean store. Give us more info: was this atti mode? Did you go into tripod mode?
The store was brand new, opening the day after my flight. People are workers stocking the shelves. Of course I had the prop guards on for safety. Absolutely no GPS because of the building's metal roof. The downward sensor locked on to the floor some of the time (ie only if there was a pattern, with a solid color it didn't) A floor lock was required to make 360° panos. One of the hazards of indoor flight is ventilation systems. They will blow the drone around. I didn't use tripod mode however it probably would have made the video smoother. I was actually very surprised when I asked the manager if I could fly in the store and he said "Yes". I've been flying since 2012 and all of my early stuff was simple without GPS or sensors, ie ATTI mode. Flying ATTI mode in the wind is a great skill builder.
