The 'estimateE​ssentialMa​trix' function cannot uniquely obtain the E matrix

I'm trying the Structure from Motion.

I am using the estimateEssentialMatrix function to estimate the essential matrix (E matrix), but I cannot uniquely obtain the E matrix.

The output result changes every time I run the program.

I tried various values ​​of MaxNumTrials, Confidence, and MaxDistance, but I could not find them uniquely.

The number of corresponding points (matchedPoints) used in the calculation is about 15. Is this because there are too few points?

If you have any idea about the cause of the problem, thank you.