Is it error in Sage or mwrank
Sage is unable to compute generators of this elliptic curve:
E=EllipticCurve([0,0,0,-3904/3,-144025/27])
E.gens()
The curve has quite small point (-1373/300, 22927/1000).
Is it error in Sage or in mwrank algorithm?
EDIT: Another example:
E=EllipticCurve([0,0,0,-106/3, -911/27])
E.gens()
It has small point: (-7/3, -6).
Sage is terrible.
The more diplomatic ,specific, and constructive version of your "sage is terrible" would be: "It looks like there are many opportunities to make "E.gets()" succeed on a lot more elliptic crurves."
It does look like a lot of the higher descent techniques (and 3-descent) that are available in magma, aren't available in sage. It's hard to find someone motivated to do the hard work again -- the first time (for the implementation in magma) the author got a nice paper out of it. That's hard to replicate for the person who'd implement these routines in sage.