Who knows. Could have been a bad install. Or the flooring wasn't acclimated to the room. Cheap import/ bad milling. Improper climate control...

I don't think there is a fix other than replacing it. Hopefully you don't have a house full of this?

Wood shrinks only a tiny amount in the direction of the grain, at least 10x more across the grain. What you see is how the flooring was laid, not the result of subsequent movement.

The regularity of that suggests it is a synthetic product like plywood or another "engineered" material rather than hardwood-- which makes it even less likely to be shrinkage.

Looks like a vinyl floor badly laid.

It could be any number of issues. Likely you will end up replacing that floor if its too much of an eyesore.

The beveled edge is helping to create the visual eye sore. The short ends are the worst part of the install which is made to look WORSE because the floor is not laid in the direction of the sunlight. It is parallel to the sunlight which means each edge is 'back lit' ... making everything look worse that it is.