Others will have more experience here, but have you tried a simple square?

Things I'm thinking - superficially, at least, it looks like you might be losing steps in the x-axis, but I don't know/can't rule out if aspire has a mach3 post-processor and/or if arcs could be causing an issue?, If you repeat the test with a simple 40x40mm square then at least you can start to understand if you're losing steps due to acceleration or max feed rate. When calibrating my machine I usually run a 40mm square with diagonals routed as well (a X in a box) just to get a visual on linearity, etc.