Every time I have experienced a situation where I was falling or when the ground would disappear under me it had to do with issues with grounding. If you are afraid of heights or if you have overly active fear of death or if you are unaware of how you are connected to a ground level metaphysically then it is easy to be affected by these types of situations in dreamtime.
I suggest you connect with the earth and get a good sense of the omniscience that the planet actually has as a living sentient being. Ground yourself everyday with a golden grounding cord to the center of the planet or by sending golden rings down from Source energy around down to the center of the planet.
Understand that you are in a self perpetual toroidal field and the earth is also a toroidal field. The earth is also alive and you can commune with the planet with the love in your heart chakra from Gaia to stay grounded.
So when you are in these dreamtime scenarios you know regardless you are always on earth with a solid ground under you. If you were to fall you know that you have a solid core toroidal energy field under you that superimposes as your plane of existence just like the physical earth plane and it is the same physics you are made up out of.
It can also help to work with the root chakra with the base survival aspects of making your space to live more energetically secure and keeping that feeling of grounded safety within you when you are out and about in your town.
Here's a video I did about a year ago on keeping your ground and constantly raising your vibration out of lower frequency:
https://youtu.be/_G3cC6yioVY
Hope this helps