There's no easy way to say this, but you may have bought an incorrect robot vacuum.
Generally, there are 3 different kinds of robot vacuums: dumb, kinda smart, truly smart.
Their prices vary widely, so cheap robots don't automatically mean it is dumb. An expensive robot also doesn't always mean it is smart. For example, a smart xiaomi robot vacuum usually priced around the same as a dumb roomba.
So if you were wondering, why your robot vacuum keeps crashing into things, gets stuck, and falling off stairs... You may need to consider buying a more appropriate robot vacuum.
What kind of robot vacuum did I have?
The easiest way to find that out is by checking your robot vacuum's sensors. If it doesn't have a camera and/or LIDAR (the cylindrical thing on top of your robot). Then it is a dumb robot.
A dumb robot vacuum is only good for cleaning 1 room.
If it has a camera but no LIDAR, then you got a kinda smart robot vacuum. This robot vacuum is able to clean multiple rooms in one go and automatically return to its dock. Some brands (xiaomi/mijia, dreame, etc) also equipped this kind of robot vacuum with the ability to be blocked from entering certain areas/room. But because it only have 1 camera facing the ceiling, it will still bump into things.
A kinda smart robot vacuum cleaner is good for cleaning a small apartment.
On the other hand, if your robot vacuum got a cylindrical thing on top of it, you got a truly smart robot vacuum. It won't bump into things (most of the time), it can clean multiple rooms without any issue, and you can prohibit it from cleaning up certain areas or rooms. Some brands (roborock, etc) also added a camera or two on their smart robot vacuums, allowing them to recognize objects and avoid them. Really useful for pet owners, as the robot is able to avoid poop on the floor.
A truly smart robot vacuum cleaner is a delight to have for a large house, no matter how many rooms you have.
What robot vacuum cleaner I should buy?
You need to ascertain what do you want the robot vacuum to do, and consult trustworthy websites like Smart Robot Reviews. It have a handy search and filters where you can easily look for the appropriate robot vacuum (and mop) for your needs.
Full disclosure: redder is not affiliated with Smart Robot Reviews. Their website simply is the best in providing good information for anyone looking to buy a robot vacuum cleaner.