I just bought an intex SX2800 sand pump put it together and it’s leaking right where the pre filter meets the motor control. I have reassemble 3 times and it’s not getting any better or worse the O rings are in place and are in perfect condition. It seems to be missing an o ring maybe in the second pic 
That is unfortunate. Did you get it resolved? Seems like a solid warranty replacement if you ask me. You shouldn't have to be messing with a brand new pump like that, especially in that location.