One explanation might be that the installer did not follow the old rule of wood floor installation, which is to allow the flooring to sit in the room for a number of days to acclimate to the room's humidity level. After installation, the flooring contracted (i.e., shrunk), causing these gaps.
But engineered flooring is often called dimensionally stable, which translates to: the plywood sandwich helps prevent many of the problems of solid hardwood, such as moisture problems. In other words, you don't expect engineered wood to contract a quarter-inch.
It could be that, in combination with some slight contraction, the engineered flooring simply wasn't fitted together tight enough. Tongue-and-groove floorboards do need to be gently tapped in place.
But that's all water under the bridge. The question is: What to do?
Determine how the boards are joined. Does this happen to be a "click and lock" type of engineered flooring? Is it tongue-and-groove? Are they glued together? You say this is a floating engineered floor, so that means that it is not joined to the subfloor. If the flooring happens to be the "click and lock" type, then you can even re-install it. Or, should you decide to call in the warranty, this is another possibility, though be prepared for losing one year of pro-rated value on the flooring (that's how most flooring warranties are written).