Robot error: “robot seems to be out of the pool”

[Brandi!!]

Anyone familiar with this error message on a Dolphin M400? I would assume it has something to do with water flow. I’ve checked the rollers and the propeller. I can’t google or troubleshoot/Faq through Dolphin an answer.
I turn it on. It runs for a few minutes to an hour and then gives me this error message. It does clean and pick up debris during that time.

 

[wireform]

I would possibly interpret "robot out of pool" to be associated with the pump motor sensor not sensing resistance of the water passing through the fan blade. Not enough resistance = not in the water.

 

[Brandi!!]

Thank you. Any cause that you could think of that would create this reduction or perceived reduction?

 

[wireform]

Here's one more idea. There's a rubber or plastic flap on the bottom where the water drains from when it's pulled out of the water. Possibly it isn't completely clipped on and water can get sucked into the robot bypassing the filer mimicking less resistance on the fan blades as it's not pulling the water through the filters = less resistance.
It may look like THIS or similar.